unit 7 ionic bonding

Unit 7

Ionic Bonding Table of Contents

Table of Contents 1

Introduction 3

Essential Questions 4

Review 4

Lesson 7.1: Formation of Ions 6 Objectives 6 Warm-Up 6 Learn about It 7 Key Points 16 Web Links 16 Check Your Understanding 17 Challenge Yourself 17

Lesson 7.2: Ionic Compounds 19 Objectives 19 Warm-Up 20 Learn about It 22 Worked Examples 27 Key Points 30 Web Links 30 Check Your Understanding 31 Challenge Yourself 32

Lesson 7.3: Naming and Writing Ionic Compounds 33 Objectives 33 Warm-Up 33 Learn about It 34

Worked Examples 35 Worked Examples 38 Worked Examples 43 Worked Examples 47 Key Points 49 Web Links 50 Check Your Understanding 50 Challenge Yourself 51

Lesson 7.4: Properties of Ionic Compounds 52 Objective 52 Warm-Up 52 Learn about It 53 Key Points 56 Web Links 56 Check Your Understanding 57 Challenge Yourself 57

Laboratory Activity 58

Performance Task 60

Self Check 62

Key Words 63

Wrap Up 64

Photo Credits 64

References 64

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GRADE 9 | SCIENCE

Unit 7 Ionic Bonding

Elements combine to form compounds. These compounds have different properties from the properties of the individual elements they are made of. For example, sodium is a very reactive metal. It explodes when it is in contact with water. Chlorine is a poisonous green gas. However, when sodium and chlorine combine they form crystals of sodium chloride. Also known as table salt, sodium chloride is an edible compound used in cooking. Studying how compounds are formed is essential in understanding the properties and uses of compounds. The properties of a substance depends on the type of bond that hold their atoms together. The atoms in the sodium metal are held by metallic bonds. The atoms in the chlorine gas are held by covalent bonds. The atoms in sodium chloride are held by ionic bonds. As explained in the previous lessons, these bonds are formed from


the interactions of the valence electrons. The valence electrons in each type of bonds interact differently, giving the molecules different properties. In this unit, you will be introduced to a type of bond known as ionic bond. By studying how this type of bond is formed, we will be able to explain the properties of sodium chloride and other ionic compounds.

Essential Questions

At the end of this unit, you should be able to answer the following questions.

● How are ionic compounds formed? ● What are the general properties of ionic compounds? ● Why is sodium chloride brittle, and why does it dissolve in water?

Review

● An element is composed of only one kind of atom. It is the simplest form of pure substance. It can be classified as metals, nonmetals, and metalloids.


○ Metals are found in the left part of the periodic table. Some examples are K, Mg, and Zn.

○ Nonmetals are found in the right part of the periodic table. Some examples are Cl, C, and O.

○ Metalloids are found in between metals and nonmetals. Some examples are Si, Ge, and As.

● A compound is a composed of two or more elements combined chemically. It also has a fixed proportion by mass. The combination of elements forms a new substance.

● When atoms bond together, their valence electrons participate in the formation of chemical bonds.

● In a Lewis electron-dot symbol, valence electrons are represented as dots around the element symbol.

● According to the octet rule, an element that has a total of 8 valence electrons is inert. Hence, an element must achieve the octet by either losing, gaining or sharing its valence electrons.


Lesson 7.1: Formation of Ions

Objectives In this lesson, you should be able to:

● discuss how ions are formed; and ● predict the charge of an atom when it is transformed to an ion.

Atoms are the building blocks of matter. It is composed of fundamental particles namely protons, electrons, and neutrons. The protons are positively-charged, while the electrons are negatively-charged. A neutron is uncharged. For an atom to be neutral, it should contain the same number of protons and electrons. Have you ever wondered what will happen when the number of protons and electrons are not equal?

Warm-Up

Are Bohr and Lewis friends? Using a periodic table, fill up the table that follows. On the second column, write the element’s electron configuration. Then, on the third column, draw the Bohr atomic model. Lastly, on the fourth column, draw the Lewis electron-dot symbol. Answer the questions that follow.

Element Electron

configuration Bohr atomic model

Lewis electron-dot model

Na


Cl

Guide Questions:

1. Are the two representations the same? How are they different? 2. Sodium is a metal. Based on its models, how can it satisfy octet rule? On the

other hand, chlorine is a nonmetal. Based on its models, how can it satisfy octet rule?

3. After satisfying the octet, how does the number of electron in sodium compares to its number of protons? What can you say about its charge? How about for chlorine?

Learn about It

Neutral Atoms and Ions Inside the nucleus are protons and neutrons. A proton is a positively-charged particle while a neutron is a neutrally-charged particle. The number of protons in an element corresponds to the atomic number (Z) of an element. The sum of protons and neutrons of an element is equal to the mass number (A) of an element. Revolving around the nucleus are negatively-charged particles called electrons.

Fig.1. A condensed model of an atom. The neutrons and protons comprise the

nucleus.


When an atom has an equal number of protons and electrons, the atom is considered a neutral atom. Hence, atomic number is also equal to the number of electrons. When an atom gains or loses an electron, the atom has a net electric charge. An electrically charged atom or group of atoms is called an ion. When the ion is composed only of one atom, it is called a monoatomic ion. When the ion is composed of two or more atoms, it is called a polyatomic ion. In an ion, the number of protons remains the same. However, since the electrons are added or removed from an atom, the number of electrons is different from the number of electrons in a neutral atom. Only valence electrons are added or removed from an electron. Recall that valence electrons are electrons found in the outermost shell. An ion can be classified as a cation or an anion.

Fig. 2. Classification of ions.

Cation When an atom loses an electron, there will be a greater number of protons than electrons. The atom becomes a positively charged ion called as a cation. Metals have a greater tendency to lose electrons. They lose a certain number of electrons to have the same number of electrons as that of the nearest noble gas. This change in the number of electrons makes the atom stable. Metals forms cations when it loses an electron.


Group 1 Elements Let’s take a look at sodium, a group 1 metal. Since sodium (Z = 11) is a metal, there is a greater tendency for sodium to lose an electron. When sodium loses an electron, it produces a sodium cation (Na+) which has a charge of +1. The removal of an electron makes sodium more positive. After the removal of an electron, the number of electrons in Na+ becomes 10. This is also the same number of electrons for neon (Ne), the nearest preceding noble gas to sodium.

Fig. 3. Sodium loses one electron to produce a sodium cation.

Notice that Na+ and Ne have the same electron configuration. Hence, they are isoelectronic. Ne has an electron configuration of 1s2 2s2 2p6. Metals within the same group have the same tendency to lose electrons. For example, all elements in group 1 including hydrogen lose one electron. They form cations with +1 charge. Cations with +1 charge are called monovalent cations. This also applies to metals in other groups as you can see in the following discussions. Group 2 Elements Now, let’s take a look at magnesium, a group 2 metal. Since magnesium (Z = 12) is a metal, there is a greater tendency for magnesium to lose electrons. Since it belongs to Group 2, it loses two electrons to produce a magnesium cation (Mg2+) which has


a charge of +2. This is also isoelectronic to neon since they have the same number of electrons.

Fig. 4. Magnesium loses two electrons to produce a magnesium cation.

All elements in group 2 lose two electrons and form cations with +2 charge. Cations with +2 charge are called divalent cations. Group 3 Elements Now, let’s take a look at aluminum, a group 3 metal. Since aluminum (Z = 3) is a metal, there is a greater tendency for aluminum to lose electrons. Since it belongs to Group 3, it loses three electrons to produce an aluminum cation (Al3+) which has a charge of +3. This is also isoelectronic to neon since they have the same number of electrons.


All elements in group 3 lose three electrons and form cations with +3 charge. Cations with +3 charge are called trivalent cations. In general, the number of electrons lost by a metal is equal to its group number. The table below shows the charges of the ions formed by metals belonging in a specific group number.

Table 7.1. Number of electrons lost by metals. Group Metals No. of Electron Lost Charge

1 Li, Na, K 1 electron +1 2 Be, Mg, Ca, Sr, Ba 2 electrons +2 3 B, Al, Ga, In 3 electrons +3 4 C, Si 4 electrons +4

Transition metals also lose electrons. However, the number of electrons they lose varies. For example, silver (group 11) loses one electron. Zinc and cadmium (group 12) lose two electrons. Iron can lose two or three electrons. A portion of the periodic table below shows common ions formed by transition metals.


Fig. 6. Ions commonly formed by transition metals.

Anion When an atom gains an electron, there will be a greater number of electrons than protons. The atom becomes a negatively charged ion called as an anion. Nonmetals have a greater tendency to gain electrons. They only need to accept few electrons to have the same number of electrons as that of the nearest preceding noble gas. Hence, making the anion of nonmetals stable. Nonmetals form anions when it gains an electron. Group 17 Elements Let’s take a look at chlorine, a group 17 element. Since chlorine (Z = 17) is a nonmetal, there is a greater tendency for chlorine to gain an electron. When chlorine gains an electron, it produces a chlorine anion (Cl-) which has a charge of -1. The addition of an electron makes chlorine more negative. After the addition of an electron, the number of electrons in Cl- becomes 18. This is also the same number of electrons for argon (Ar), the nearest succeeding noble gas to chlorine. Therefore, chlorine ion and argon are isoelectronic.


Fig. 7. Chlorine gains an electron to produce the chlorine anion.

This also applies to nonmetals in other groups as you can see in the following discussions. Group 16 Elements Let’s take a look at sulfur, a group 16 element. Since sulfur (Z = 16) is a nonmetal, there is a greater tendency for sulfur to gain electrons. Since it belongs to Group 16, it gains two electrons to produce a sulfur anion (S2-) which has a charge of -2. This is also isoelectronic to argon since they have the same number of electrons.


Fig. 8. Sulfur gains two electrons to produce the sulfur anion.

All elements in group 16 lose two electrons and form anions with -2 charge. Anions with -2 charge are called divalent anions. Group 15 Elements Let’s take a look at phosphorus, a group 15 element. Since phosphorus (Z = 15) is a nonmetal, there is a greater tendency for phosphorus to gain electrons. Since it belongs to Group 16, it gains three electrons to produce a phosphorus anion (P3-) which has a charge of -3. This is also isoelectronic to argon since they have the same number of electrons.


Fig. 9. Phosphorus gains three electrons to produce the phosphorus anion.

All elements in group 15 lose three electrons and form anions with -3 charge. Anions with -3 charge are called trivalent anions. In general, the number of electrons gained by a metal can be identified its group number. The table below shows the charges of the ions formed by nonmetals belonging in a specific group number.

Table 7.2. Number of electrons gained by nonmetals. Group Nonmetals No. of Electron Gained Charge

15 N, P 1 electron –3 16 O, S, Se, Te 2 electrons –2 17 F, Cl, Br, I 3 electrons –1


Key Points

● An electrically-charged atom is called an ion. It could be a monoatomic ion or

polyatomic ion. ● An ion can be classified as a cation or an anion.

○ A positively-charged ion called as a cation. ○ A negatively-charged ion called as an anion.

● Metals tend to lose electrons and produce cations. Nonmetals tend to gain electrons and produce anions.

● Ions produced by losing or gaining electrons has the same electron configuration to the nearest noble gas. Hence, they are isoelectronic.

Web Links

For further information, you can check the following web links:

● The formation of ions explained in nice illustrations here in this video: Binogi. 2016. ‘Atoms Form Ions (Chemistry).’ https://www.youtube.com/watch?v=x4IoMrlths0

● Ions are actually our body’s own way of communication. Click this site to know more: Universität Bern. 2014. ‘Ion Channels: How Your Body Communicates.’ https://www.youtube.com/watch?v=_icBM60sMOU


https://www.youtube.com/watch?v=x4IoMrlths0

https://www.youtube.com/watch?v=x4IoMrlths0

https://www.youtube.com/watch?v=_icBM60sMOU

https://www.youtube.com/watch?v=_icBM60sMOU

● Ions in the environment, how do they affect us? Look at what their study showed: TrionZLive. 2013. ‘The Effects of Positive & Negative Ions.’ https://www.youtube.com/watch?v=XvLmwgZWTdM

Check Your Understanding

A. Fill up the table below. On the first column, identify if the following elements

tend to lose or gain electrons. Write cation if the element tends to lose electrons. Otherwise, write anion if the element tends to gain electrons. Then, identify the number of electrons the atom accepts or gains. Lastly, write the symbol of the ion.

Atom Type of ion Number of electrons

lost/gained

Ion symbol

Li

S

N

Ca

Rb

Mg

Se

Challenge Yourself

1. Can noble gases form ions? Why or why not?


https://www.youtube.com/watch?v=XvLmwgZWTdM

https://www.youtube.com/watch?v=XvLmwgZWTdM

2. Nonmetals tend to accept electrons and form anions. Where do you think these electrons come from?

3. Which do you think is larger, a cation or an anion? In terms of size, how does each ion compare to a neutral atom?

4. Copper, iron and zinc are transition metals and can form Cu2+, Fe2+ and Zn2+ ions. Why are +2 ions common in transition metals?

5. Why can some ions form multiple charges?


Lesson 7.2: Ionic Compounds


● discuss the formation of ionic compounds; and ● determine the formula of simple ionic compounds using the

crisscross rule.

The table salt used in cooking, the limestone present in cement, and baking soda used in baking pastries are examples of ionic compounds. Ionic compounds are compounds formed by the reaction of a cation and an anion. Several ionic compounds are used in daily life. Have you ever wondered how ionic compounds are formed?

Table salt


Cement in concrete

Baking soda

Fig. 10. Some ionic compounds used in everyday lives.

Warm-Up

I’ve got my ION you!

Look at the cards below. Each cards contain neutral atoms represented by chemical symbols. Then, identify the ion that can be formed from the element. Recall that metals form cations while nonmetals form anions.


Identity of the ion that can be formed: _______________





Learn about It

Ionic Compounds An ionic compound is formed by the combination of cations and anions. An electrostatic attraction is formed when cations and anions combine. The force which holds together cation and anion in a compound is known as an ionic bond. A binary ionic compound is composed of a metal and a nonmetal in an ionic bond. In forming an ionic bond, metals lose electrons to form cations while nonmetals gain electrons to form anions. The electron lost from the cation formed is transferred to the anion. Hence, an ionic compound is made up of metals and nonmetals. Binary Ionic Compounds from Group 1 and Group 17 elements Let us take for example the formation of sodium chloride. Sodium chloride or table salt is a common ingredient in cooking. Salt is made up of sodium, a metal and chlorine, a nonmetal. Sodium is a group 1 element and tends to lose one electron. Chlorine is a group 17 element and tends to gain one electron. The electron that the sodium atom loses will be transferred to the chlorine atom. Thus, the sodium cation and chlorine anion are isoelectronic with the noble gases neon and argon respectively.

Fig. 11. Formation of sodium chloride.


To determine the chemical formula, use the crisscross rule. In the crisscross rule, the superscript of the cation becomes the subscript of the anion. The superscript of the anion becomes the subscript of the cation. When the subscript is one, the number 1 is usually not written. The formula can be simplified by dividing the subscript by the same number when needed. Subscripts can only be whole numbers. Since there are one sodium cation and one chlorine atom, the chemical formula for sodium chloride is NaCl. Using the crisscross rule, the same chemical formula is also obtained.

Ionic compounds are electrically neutral. The number of positive charges should be equal to the number of negative charges. For example, sodium ion has a charge of +1 while chlorine ion has a charge of -1. There is an equal number of positive and negative charges which resulted to an electrically neutral sodium chloride. Binary Ionic Compounds from Group 2 and Group 16 elements Now, let us look at the formation of magnesium sulfide. Magnesium sulfide is used as a component of semiconductors and LED lights. It is made up of magnesium, a metal and sulfur, a nonmetal. Magnesium is a group 2 element and tends to lose two electrons. Sulfur is a group 16 element and tends to gain two electrons. The electrons that the magnesium atom loses will be transferred to the sulfur atom.


Thus, the magnesium cation and sulfur anion are isoelectronic with the noble gases neon and argon respectively.

Fig. 12. Formation of magnesium sulfide.

By using the crisscross formula, the charge of the magnesium cation becomes the subscript of the sulfur anion. The charge of the sulfur anion becomes the subscript of the magnesium cation. By simply following these rules, the chemical formula of magnesium sulfide is Mg2S2. This can be simplified by dividing the subscripts by their least common multiple. You can think of the subscripts as a ratios of one atom to the other, which can be expressed in lowest term. The chemical formula of magnesium sulfide, then, is MgS.

Binary Ionic Compounds from Group 3 and Group 15 elements This time, let us look at the formation of aluminum phosphide. Magnesium sulfide is used as a component of rodent pesticides. It is made up of aluminum, a metal and phosphorus, a nonmetal. Aluminum is a group 3 element and tends to lose three electrons. Phosphorus is a group 15 element and tends to gain three


electrons. The electrons that the aluminum atom loses will be transferred to the phosphorus atom. Thus, the aluminum cation and phosphorus anion are isoelectronic with the noble gases neon and argon respectively.

Fig. 13. Formation of aluminum phosphide.

By using the crisscross formula, the charge of the aluminum cation becomes the subscript of the phosphorus anion. The charge of the phosphorus anion becomes the subscript of the aluminum cation. By simply following these rules, the chemical formula of aluminum phosphide is Al3P3. Again, this can be simplified by dividing the subscripts by their least common multiple. The chemical formula of magnesium sulfide is AlP.


Binary ionic compounds formed by combining other elements This time, let us consider barium chloride. It is made up of barium, a metal and chlorine, a nonmetal. Barium is a group 2 metal and tends to lose two electrons while chlorine is a group 17 nonmetal and tends to gain one electron. Since one chlorine atom can only gain one electron, a second chlorine atom is needed to transfer the two electrons that barium loses completely.

Barium has a charge of +2 while chlorine has a charge of -1. There are one barium atom and two chlorine atoms that participated in the formation of barium chloride. Using the crisscross rule, the formula for barium chloride is BaCl2.

This shows that ionic compounds can be formed even if the electrons lost by the cation is not equal to the electrons gained by the anion. Representative elements can form multiple ionic compounds as long as metals (groups 1, 2, and 13) combine


with nonmetals (groups 15, 16, and 17). For example, metals in group 1 can form ionic compounds with nonmetals in group 15. The table below lists down possible combinations of ionic compounds and its chemical formula. Metals are represented by the symbol M while nonmetals are represented as X.

Table 7.3. General formula of ionic compounds. Metal Group Nonmetal Group General Formula Example

1 17 MX NaCl 2 17 MX2 CaCl2

13 17 MX3 AlCl3 1 16 M2X Li2O 2 16 MX CaO

13 16 M2X3 Al2O3 1 15 M3X Na3P 2 15 M3X2 Ca3P2

13 15 MX AlN

Worked Examples

Example 1 Write the chemical formula for the ionic compound lithium fluoride. Solution Step 1 Identify the cation and the anion.

The cation is always written first in the chemical name. The anion is written last. Hence, the compound lithium fluoride is composed of a lithium cation and a fluorine anion.

Step 2 Identify the chemical symbol and charge of each ions.

Use the group number to identify the charge of representative elements. Li is in group 1 and forms a +1 cation. F is in group 17 and forms a -1 anion.

Step 3 Use the crisscross method to determine the chemical formula of the


compound. The charge of the cation becomes the subscript of the anion, and the charge of the anion becomes the subscript of the cation.

Therefore, the chemical formula for lithium fluoride is LiF.

Let us Practice Write the chemical formula of the ionic compound potassium iodide.

Example 2 Write the chemical formula for the ionic compound barium sulfide. Solution Step 1 Identify the cation and the anion.

The cation is always written first in the chemical name. The anion is written last. Hence, the compound barium sulfide is composed of a barium cation and a fluorine anion.


Use the group number to identify the charge of representative elements. Ba is in group 2 and forms a +2 cation. S is in group 16 and forms a -2 anion.

Step 3 Use the crisscross method to determine the chemical formula of the compound. The charge of the cation becomes the subscript of the


anion, and the charge of the anion becomes the subscript of the cation.

The resulting subscripts after applying the crisscross formula can be further simplified by dividing both of them by two (2). Therefore, the chemical formula for barium sulfide is BaS.

Let us Practice Write the chemical formula for the ionic compound aluminum arsenide.

Example 3 Write the chemical formula for the ionic compound aluminum chloride. Solution Step 1 Identify the cation and the anion.

The cation is always written first in the chemical name. The anion is written last. Hence, the compound aluminum chloride is composed of an aluminum cation and a chloride anion.


Use the group number to identify the charge of representative elements. Al is in group 3 and forms a +3 cation. Cl is in group 17 and


forms a -1 anion.

Step 3. Use the crisscross method to determine the chemical formula of the compound. The charge of the cation becomes the subscript of the anion, and the charge of the anion becomes the subscript of the cation.

Key Points

● An ionic compound is formed by the combination of cation and anion. It

involves transfer of electrons form a metal to a nonmetal. ● The force which holds together cation and anion in a compound is known as

an ionic bond. ● The charge of an ion formed from a representative element can be

determined using its group number. ● The final formula of the compound can be determined using the crisscross

formula. The charge of the cation becomes the subscript of the anion, while the charge of the anion becomes the subscript of the cation.

Web Links



● How are ionic bonds formed? Visit this site to know the fundamentals of ionic bonding: FuseSchool - Global Education. 2013. ‘What are Ionic Bonds? | The Chemistry Journey.’ https://www.youtube.com/watch?v=zpaHPXVR8WU

● Important ions and ionic compounds inside our body: what you should not lose in your diet? http://wpscms.pearsoncmg.com/wps/media/objects/1053/1078874/ist/blue0201.html

● If you take water out of saltwater, what will you be left with? Find out here if the answer is NaCl: The King of Random. 2017. ‘What Happens when You Boil the Ocean?’ https://www.youtube.com/watch?v=gZQbQohCEW0


A. Write ionic if the following combination of elements will result in an ionic

compound. Otherwise, write not ionic. Write the chemical formula for ionic compounds.

1. magnesium and chlorine 2. sodium and silicon 3. calcium and bromine 4. selenium and nitrogen 5. carbon and oxygen 6. aluminum and oxygen 7. fluorine and cesium 8. lithium and nitrogen 9. silicon and hydrogen 10.oxygen and chlorine

B. Use the Lewis electron-dot symbol to show how electrons are transferred

between the following atoms. 1. Na and Br 2. Sr and N


https://www.youtube.com/watch?v=zpaHPXVR8WU

https://www.youtube.com/watch?v=zpaHPXVR8WU

http://wpscms.pearsoncmg.com/wps/media/objects/1053/1078874/ist/blue0201.html



https://www.youtube.com/watch?v=gZQbQohCEW0

https://www.youtube.com/watch?v=gZQbQohCEW0

3. K and S 4. Al and O 5. Ca and Cl

C. Fill up the table by indicating the missing ions or compounds.

Cations

Anions Fr+ Sr2+ Al3+

I-

O2-

P3-

Challenge Yourself

Briefly explain what is asked.

1. A hydride ion is produced when a hydrogen atom gains an electron. This ion is found in several compounds such as lithium hydride (LiH) and calcium hydride (CaH2). Similarly, hydrogen ion can form a cation by losing an electron. It is usually found in acids. Explain why hydrogen can form stable ions by either losing or gaining one electron.

2. Explain why charges above +3 are uncommon for representative metals. 3. Use the Lewis electron-dot symbol to show how electrons are transferred

between Zn and Cl ions. 4. Agua oxigeneda is a relatively stable compound which is used to clean and

treat wounds. Its chemical formula is H2O2. Identify the ions present in this compound.

5. Salitre is a colorless salt used as preservatives in meat. Its chemical formula is Na3N. Identify the ions present in this compound.


Lesson 7.3: Naming and Writing Ionic Compounds


● give the correct name and write the formula for binary ionic compounds;

● use the classical and stock systems to name ionic compounds containing metal cations of variable charge;

● give the correct name and write the formula for ternary ionic compounds; and

● give the correct name and write the formula for hydrates.

Every object, place, and person have its own name which makes it identifiable from the others. Similarly, every compound has its own unique name which helps it to be distinct from the existing millions of compounds. Hence, there should be a set of rules in naming compound to be systematic. Have you ever wondered how to name ionic compounds?

Warm-Up

Draw and Match Shown below are six cards representing six different elements. Identify whether each element forms a cation or an anion. Write the chemical symbol of the ions in the table below. Then, create at least three ionic compounds from your set of ions. Write the chemical name on the last column of the table provided below.


Cations Anions Ionic Compound

Learn about It


The study of naming compounds is known as chemical nomenclature. The word nomenclature comes from two Latin words nomen meaning “name” and calare meaning “to call”. Naming compounds is one of the necessary skills in chemistry. The name of a given compound can give ideas on its composition and possible properties. Naming and Writing Binary Ionic Compounds A binary ionic compound consists of one metal and one nonmetal. As a general rule in naming binary ionic compounds, follow the steps below.

1. The metal is designated as the cation. The name of the metal retains its name in forming a binary ionic compound. For example, if the metal in the ionic compound is sodium, the word “sodium” is used in naming.

2. The nonmetal is designated as the anion. Change the name of the nonmetal ending in —ide. For example, if the nonmetal in the ionic compound is chlorine, the word “chloride” is used in naming.

Worked Examples

Example 1 Write the chemical name for the compound RbBr. Solution Step 1 Identify the cation and anion present in the compound.

The cation is written first and the anion is written last. For this compound, the cation is Rb while the anion is Br.

Step 2 Identify the charges by reversing the crisscross process.

In a reverse crisscross, the subscript of the anion becomes the charge of the cation while the subscript of the cation becomes the charge of the anion. Since the anion Br has no subscript, the charge of Rb is +1. Also, the cation Rb has no subscript, the charge of Br is -1.

Step 3 Name the ions accordingly, then properly name the compound.


Rb+ is rubidium ion, while Br- is bromide ion. Therefore, the chemical name of RbBr is rubidium bromide.

Let us Practice Write the chemical name for the compound KI.

Example 2 Write the chemical formula for the compound strontium chloride. Solution Step 1 Identify the cation and anion present in the compound.

The cation is written first and the anion is written last. For this compound, the cation is strontium while the anion is chloride.

Step 2 Write the chemical symbol and identify its charge.

The charge of the ions to be formed is based on their group number in the periodic table. Sr is a group 2 element, and produces a +2 cation. Cl is a group 17 element and produce a -1 anion.

Step 3 Use the crisscross formula to determine the chemical formula of the

compound. In the crisscross process, the charge of the cation becomes the subscript of the anion, and the charge of the anion becomes the subscript of the cation. By applying this formula, the formula of the resulting compound is SrCl2. Therefore, the chemical formula of strontium chloride is SrCl2.

Let us Practice


Write the chemical name for the compound calcium iodide

The above-mentioned rule is generally applicable for metals which have a fixed charge. Those metals have only the capacity to lose a fixed number of electron in forming all possible ionic compounds. Metals with fixed charges are listed in Table 3.

Table 3. Metals with fixed charges. IA IIA IIIA IVA VA VIA VIIA IB IIB +1 +2 +3 +4 -3 -2 -1 +1 +2 Li Na K

Be, Mg Ca, Sr

Ba

B Al

C Si

N P

O S Se

F, Cl Br, I

Ag Zn, Cd

For metals with multiple charges and a nonmetal, there are two ways of naming compounds: by the classical system or by the stock system.

1. The classical system is mostly for elements having Latin names and have two possible charges. Instead of retaining the name of the metal, the Latin name of the metal is used ending in —ous or —ic. Nonmetals still end in —ide. The suffix —ous is used if the metal has a lower charge while the suffix —ic is used if the metal has a higher charge. For example, Cu+ is written as cuprous while Cu2+ is written as cupric.

2. The stock system uses Roman numerals to identify the charge of the metal with two or more possible charges. The name of the metal is retained while adding the charge in Roman numerals within a parenthesis after the name of the metal. Nonmetals still end with —ide. For example, Cu+ is written as copper (I) while Cu2+ is written as copper (II).

Table 4 lists down some elements with multiple charges. Metals with multiple charges are commonly found in the transition metals group.

Table 4. Metals with multiple charges. English Name Latin Name Symbol Higher Charge Lower Charge

Iron Ferrum Fe Fe3+, Ferric Fe2+, Ferrous


Tin Stannum Sn Sn4+, Stannic Sn2+, Stannous Copper Cuprum Cu Cu2+, Cupric Cu+, Cuprous

Lead Plumbum Pb Pb4+, Plumbic Pb2+, Plumbous Mercury Hydrargyrum Hg Hg2+, Mercuric Hg2

2+, Mercurous Gold Aurum Au Au3+, Auric Au+, Aurous

Manganese Mn Mn3+, Manganic Mn2+, Manganous Cobalt Co Co3+, Cobaltic Co2+, Cobaltous

Chromium Cr Cr3+, Chromic Cr2+, Chromous To write formulas of binary ionic compounds, follow the steps below.

1. Write the symbol of the cation and anion. Include the electrons lost or gained as charges.

2. Crisscross the charges.

Worked Examples

Example 3 Write the chemical name for the compound CoCl3 using the stock system. Solution Step 1 Identify the cation and anion present in the compound.

The cation is written first and the anion is written last. For this compound, the cation is Co while the anion is Cl.


In a reverse crisscross, the subscript of the anion becomes the charge of the cation while the subscript of the cation becomes the charge of the anion. Since the anion Cl has a subscript of 3, the charge of Co is +3. Meanwhile, the cation Co has no subscript, the charge of Cl is -1.


The stock system uses Roman numerals to represent the charge. Hence, Co3+ is cobalt (III) ion. Meanwhile, Cl- is chloride ion.


Therefore, the chemical name of CoCl3 is cobalt (III) chloride.

Let us Practice Write the chemical name for the compound CuO using the stock system.

Example 4 Write the chemical name for the compound Fe2O3 using the classical system. Solution Step 1 Identify the cation and anion present in the compound.

The cation is written first and the anion is written last. For this compound, the cation is Fe while the anion is O.


In a reverse crisscross, the subscript of the anion becomes the charge of the cation while the subscript of the cation becomes the charge of the anion. Since the anion O has a subscript of 3, the charge of Fe is +3. Meanwhile, the cation Fe has a subscript of 2, then the charge of O is -2.


The classical system uses the suffixes -ous and -ic to represent the charge of the cation. The lower charge cation uses the suffix -ous while the higher charge cation uses the suffix -ic. Hence, Fe3+ is ferric ion. Meanwhile, O2- is oxide ion. Therefore, the chemical name of Fe2O3 is ferric oxide.

Let us Practice Write the chemical name for the compound CuO using the classical system.

Example 5


Write the chemical formula for the compound cobalt (II) sulfide. Solution Step 1 Identify the cation and anion present in the compound.

The cation is written first and the anion is written last. For this compound, the cation is cobalt while the anion is sulfur.

Step 2 Identify the chemical symbol and charge of the cation and anion.

Clues can be found from the chemical name. If the compound is named using the stock system, the roman numeral enclosed in parenthesis after the cation is the charge of the cation. The charge of the anion can be determined from its group number. Co has a charge of +2 and S has a charge of -2.

Step 3 Use the crisscross formula to determine the chemical formula of the compound. In the crisscross process, the charge of the cation becomes the subscript of the anion, and the charge of the anion becomes the subscript of the cation. By applying this formula, the formula of the resulting compound is CoS. Therefore, the chemical formula of cobalt (II) sulfide is CoS.

Let us Practice Write the chemical formula for the compound iron (II) iodide.

Example 6 Write the chemical formula for the compound cupric phosphide. Solution Step 1 Identify the cation and anion present in the compound.

The cation is written first and the anion is written last. For this compound, the cation is copper while the anion is phosphorus.


Step 2 Identify the chemical symbol and charge of the cation and anion.

Clues can be found from the chemical name. If the compound is named using the classical system, the suffix after the cation’s Latin name represents the charge of the cation. The charge of the anion can be determined from its group number. Cu has a charge of +2 and P has a charge of -3.

Step 3 Use the crisscross formula to determine the chemical formula of the compound. In the crisscross process, the charge of the cation becomes the subscript of the anion, and the charge of the anion becomes the subscript of the cation. By applying this formula, the formula of the resulting compound is Cu3P2. Therefore, the chemical formula of cupric phosphide is Cu3P2.

Let us Practice Write the chemical formula for the compound stannic nitride.

Naming and Writing Ternary and Higher Ionic Compounds A ternary ionic compound consists of two or more elements in a compound. As a general rule in naming ternary ionic compounds, follow the steps below.

1. Name the metal or the polyatomic cation. A polyatomic cation is a group containing two or more elements with a positive charge.

2. Name the nonmetal ending in —ide or the polyatomic anion. A polyatomic anion is a group containing two or more elements with a negative charge.

In NaOH, the compound contains the metal cation sodium (Na+) and the polyatomic ion hydroxide (OH-). Thus, the compound is named as sodium hydroxide. For ternary ionic compounds composed of a metal and an oxyanion, follow the steps below.


1. Retain the name of the metal. Use the classical method or stock system method if the metal has multiple charges.

2. Name the oxyanion. An oxyanion is an anion containing oxygen.

An oxyacid is an oxygen containing acid. For an oxyacid, follow the following steps below.

1. Name the polyatomic anion. Determine the polyatomic anion by removing hydrogen in the formula of the compound.

2. The name of the polyatomic anion is modified. Anions ending in —ite becomes —ous while anions ending in —ate becomes —ic. For example, the anion carbonate (CO3

2-) must be changed to carbonic when forming an oxyacid.

Table 5. List of common polyatomic ions.

Name Formula Name Formula Acetate CH3COO− Hypobromite BrO− Ammonium NH4

+ Hypochlorite ClO− Azide N3

− Hypoiodite IO− Benzoate C6H5COO− Periodate IO4

− Bicarbonate HCO3

− Iodate IO3−

Bromate BrO3− Iodite IO2

− Bromite BrO2

− Isocyanate NCO− Carbonate CO3

2− Manganate MnO42−

Chlorate ClO3− Nitrate NO3

− Chlorite ClO2

− Nitrite NO2−

Chromate CrO42− Nitronium NO2

+ Chromite CrO2

− Oxalate C2O42−

Cyanate OCN- Perbromate BrO4−

Cyanide CN- Perchlorate ClO4−

Dichromate Cr2O72− Permanganate MnO4

− Ferricyanide Fe(CN)6

3− Peroxodisulfate S2O82−

Ferrocyanide Fe(CN)64− Phosphate PO4

3− Formate HCO2

− Phosphite PO33−

Hydrogen phosphate HPO42− Silicate SiO3

2− Hydrogen phosphite HPO3

2− Sulfate SO42−

Hydrogen sulfate HSO4− Sulfite SO3

2− Hydrogen sulfite HSO3

− Tartrate C4H4O62-

Hydronium H3O+ Thiocyanate SCN−


Hydroxide OH− Thiosulfate S2O32−

To write formulas of ternary ionic compounds, follow the steps below.

1. Write the symbol of the cation and anion. Include the electrons lost or gained as charges.

2. Crisscross the charges. For polyatomic ions, the subscript is written outside of the parenthesis.

Worked Examples

Example 7 Write the chemical formula for the compound potassium nitrate. Solution Step 1 Identify the cation and anion present in the compound.

The cation is written first and the anion is written last. For this compound, the cation is potassium ion while the anion is nitrate ion.

Step 2. Determine the chemical formula using the crisscross process.

Potassium ion is written as K+ and nitrate ion is written as NO3

-. By using crisscross, the chemical formula of potassium nitrate is KNO3.

Let us Practice Write the chemical formula for the compound sodium permanganate.

Example 8 Write the chemical formula for the compound plumbous acetate. Solution Step 1 Identify the cation and anion present in the compound.


The cation is written first and the anion is written last. For this compound, the cation is plumbous ion while the anion is acetate ion.

Step 2 Determine the chemical formula using the crisscross process.

Plumbous ion is written as Pb2+ and acetate ion is written as CH3COO-. Therefore, the chemical formula of plumbous acetate is Pb(CH3COO)2.

Let us Practice Write the chemical formula for the compound ferric sulfate.

Example 9 Write the chemical formula for the compound ammonium periodate. Solution Step 1 Identify the cation and anion present in the compound.

The cation is written first and the anion is written last. For this compound, the cation is ammonium ion while the anion is periodate ion.


Ammonium ion is written as NH4

+ and periodate ion is written as IO4-.

Therefore, the chemical formula of ammonium periodate is NH4IO4.

Let us Practice Write the chemical formula for the compound sodium peroxidisulfate.

Example 10 Write the chemical name for the compound RbCN. Solution Step 1 Identify the cation and anion present in the compound.


The cation is written first and the anion is written last. For this compound, the cation is Rb while the anion is CN.


In a reverse crisscross, the subscript of the anion becomes the charge of the cation while the subscript of the cation becomes the charge of the anion. Since the anion CN has no subscript, the charge of Rb is +1. Similarly, the cation Rb has no subscript, and the charge of CN is -1.


The name of the cation is rubidium cation. Based on the table, the name of the polyatomic anion is cyanide ion. Therefore, the chemical name of RbCN is rubidium cyanide.

Let us Practice Write the chemical name for the compound AlPO4.

Example 11 Write the chemical name for the compound Sn(NO3)2. Solution Step 1 Identify the cation and anion present in the compound.

The cation is written first and the anion is written last. For this compound, the cation is Sn while the anion is NO3.


In a reverse crisscross, the subscript of the anion becomes the charge of the cation while the subscript of the cation becomes the charge of the anion. Since the anion NO3 has a subscript of 2, the charge of Sn is +2. Meanwhile, the cation Sn has no subscript, and the charge of NO3 is -1.



The name of the cation is tin (II) cation or stannous cation. Based on the table, the name of the polyatomic anion is nitrate ion. Therefore, the chemical name of Sn(NO3)2 is stannic nitrate or tin (II) nitrate.

Let us Practice Write the chemical name for the compound HgCH3COO.

Example 12 Write the chemical name for the compound (NH4)2CO3. Solution Step 1 Identify the cation and anion present in the compound.

The cation is written first and the anion is written last. For this compound, the cation is NH4 while the anion is CO3.


In a reverse crisscross, the subscript of the anion becomes the charge of the cation while the subscript of the cation becomes the charge of the anion. Since the anion CO3 has no subscript, the charge of NH4 is +1. Meanwhile, the cation NH4 has a subscript of 2, and the charge of CO3 is -2.

Step 3. Name the ions accordingly, then properly name the compound.

Based on the table, the name of the polyatomic cation is ammonium ion while the the name of the polyatomic anion is carbonate ion. Therefore, the chemical name of (NH4)2CO3 is ammonium carbonate.

Naming and Writing Hydrates


Ionic compounds may contain water molecules. Hydrates are compounds which have a specific number of water molecules attached to a given compound. In naming hydrates, the number of hydrates is added to the name of the ionic compound by using Greek prefixes together with the word hydrate.

Table 6. Greek prefix with its corresponding equivalent number. Number Greek prefix Number Greek prefix

1 mono 6 hexa 2 di 7 hepta 3 tri 8 octa 4 tetra 9 nona 5 penta 10 deca

Worked Examples

Example 12 Write the chemical name for the compound CuSO4 • 6H2O. Solution Step 1 Write the chemical formula of the ionic compound without the

hydrate. Based on our previous rules, the chemical formula for CuSO4 is copper (II) sulfate.

Step 2 Count the number of water molecules and assign the appropriate

prefix. There are six water molecules. The prefix used for six water molecules is hexa, and the name of six water molecules is hexahydrate.

Step 3 Add the name of the hydrate to the name of the ionic compound.


The complete name of the hydrated compound is the combination of the chemical name of the ionic compound and the chemical name of the hydrate.

Therefore, the chemical name for the compound CuSO4 • 6H2O is copper sulfate hexahydrate.

Let us Practice Write the chemical name for the following compounds.

Chemical Formula Chemical Name

KCl • 6H2O

AgBrO4 • 10H2O

(NH4)2SO4 • 8H2O

Example 13 Write the chemical formula for the compound sodium thiocyanate tetrahydrate. Solution Step 1 Identify the cation and anion present in the compound.

The cation is written first and the anion is written last. For this compound, the cation is sodium ion while the anion is thiocyanate ion.


Sodium ion is written as Na+ and thiocyanate ion is written as SCN-. Therefore, the chemical formula of sodium thiocyanate is NaSCN.

Step 3 Write the chemical formula for the hydrate according to the prefixes

used for the number of water molecules present.


The prefix tetra- is used to denote four water molecules.

Therefore, the chemical formula for the compound is NaSCN • 4H2O.

Let us Practice Write the chemical formula for the following compounds.

Chemical Name Chemical Name

silver chloride heptahydrate

mercurous permanganate monohydrate

ammonium cyanate trihydrate

Key Points

● The crisscross rule is used to determine the chemical formula of an ionic

compound. ● The study of naming compounds is known as chemical nomenclature. ● To name a binary ionic compound, retain the name of the metal and change

the name of the nonmetal ending in —ide. ● There are two ways of naming a metal with multiple charges: the classical

method and the stock system method. ○ In the classical method, the Latin name of the metal ends in —ous or

—ic. ○ In the stock system, Roman numerals inside the parenthesis are used

to determine the charge of the metal. ● To write formulas of ionic compounds, use the crisscross rule. ● In naming ternary and higher ionic compounds, name the metal or the

polyatomic cation and the nonmetal of the polyatomic anion. ● In naming hydrates, the number of hydrates is added to the name of the

ionic compound by using Greek prefixes together with the word hydrate.


Web Links


● Cannot memorize the names of polyatomic ions? A song might have helped you a lot: Jenny Pysh. 2016. ‘Chemistry - Memorize Polyatomic Ions to Hotline Bling Song (Chemistry Fate).’ https://www.youtube.com/watch?v=4nrrMcozp_Q

● Watch how they devise a mnemonic for polyatomic ions and see if it can help you: Chris Koder. 2012. ‘How to Remember Polyatomic Ions.’

https://www.youtube.com/watch?v=-iP2ifS4IUI


A. Write the name of the following ionic compounds.

1. CaO 2. PbSO4 3. SrO 4. CaCO3 5. KMnO4 6. HgCl 7. AgNO3 8. CaSO3 9. Co(CH3COO)3 10.AlPO4 • 4H2O

B. Write the chemical formula of the following ionic compounds.

1. magnesium chloride 2. potassium bromide 3. iron (III) oxide


https://www.youtube.com/watch?v=4nrrMcozp_Q

https://www.youtube.com/watch?v=4nrrMcozp_Q



4. plumbic selenide 5. auric nitride 6. ammonium chloride 7. sodium bicarbonate 8. potassium nitrate 9. ammonium perbromate 10.ammonium phosphate pentahydrate

C. Fill the table below.

Ions Name Chemical Formula Ca2+, Cl- Ni2+, F- Mg2+, As3- Fe3+, SO4

2- Cr3+, NO3

-

Challenge Yourself

A. Write the chemical name for the following ionic compounds:

1. AlN 2. NaO 3. Fe[(Fe(CN)6] 4. BaSO4 • ½H2O

B. Explain the following.

1. How do we come up with charges of polyatomic ions? For example, why is the charge of nitrate ion, -1?


Lesson 7.4: Properties of Ionic Compounds

Objective In this lesson, you should be able to:

● describe the properties of ionic compounds.

Have you seen certain experiments wherein citrus fruits can light up a small light emitting diode (LED)? Citrus fruits contain citric acid, an ionic compound. The mobilization of the ions in citrus makes it possible for the LED to light up. What are the properties of ionic compounds?

Warm-Up

Making an Orange Battery!

Citrus fruits such as oranges and lemons can be used to produce electricity. That is because they have molten or liquid ionic compounds inside their fruits. In this experiment, we will demonstrate how they generate electricity and how can we harness it. Materials:

● 1 piece orange or lemon


● 1 piece copper wire, at least 2 inches in length ● 1 piece iron nail, at least 2 inches in length ● 2 pieces alligator clips, length enough to reach the light bulb ● 1 piece, small light bulb

Procedure:

1. Gently roll the lemon on top of the table but do not squeeze it so tight that you break the skin.

2. Insert the copper wire and the iron nail into the lemon. Don’t puncture the other end of the lemon to prevent the juice from leaking out. The wire and the nail should not touch each other.

3. Attach one end the alligator clips to the wire and nail on the surface of the lemon.

4. Attach the other end on the small light bulb and see if it lights up.

Learn about It

Properties of Ionic Compounds Ionic compounds are generally solid at room temperature. The crystal lattices in an ionic compound are formed when cation and anion combines. The crystal lattice is made up of alternating cations and anions, as shown below.


Fig 11. The crystal lattice of an ionic compound.

The cation is smaller than the anion. This is because the neutral atom loses a shell when it transfers an electron to form a cation. Similarly, the anion is larger because the neutral atom gains a shell when it accepts an electron to form the anion. Hence, when they form the lattice, the size of each ion alternates from a cation to that of an anion. You can imagine that the packing of the ions are somehow inefficient and there are empty spaces between the ions. Although packing is not that efficient, the force that holds the ions together are very strong. If we will look closer at the structure of sodium chloride lattice, the sodium ion interacts with six chloride ions. This gives ionic solids extraordinary strength against extreme temperature changes. This explains why ionic compounds have very high boiling and melting point. High energy is needed to break the attractive forces that connect the crystal lattices. This accounts for the high boiling and melting point which involves the breaking of the forces between the molecules of a compound. However, this structured position of the anions and the cations is also the reason why ionic solids are brittle. Ionic solids are hard and requires a large amount of force to move the layer of ions. It means that there is a strong force between ions.


But when enough force is applied, the ions move in such a way that it would have the same charge with the adjacent ions causing repulsive forces to dominate.

Fig. 12. When a hammer strikes a compound, the crystal lattice is distorted,

Most ionic compounds are soluble to water. Since they are made up of charged particles, water can easily break them up. This is possible because the oxygen and hydrogen atoms are partially charged. They interact with the ions and break them out of the lattice. Moreover, ionic compounds can conduct electricity in the molten state and liquid state. When in the solid state, the ions of the compounds are held together in crystals, hence, cannot freely move. However, when it is dissolved or in the molten state, these compounds can conduct electricity because the ions, which are electrically charged particles, are free to move. For example, when sodium chloride is dissolved in water, the solution contains Na+ and Cl- ions. Both ions are free to move and since they are charged particles, they could conduct electricity. Citrus fruits such as lemons and oranges contain a lot of dissolved ions. These ions power up the light bulb you have seen on the Warm Up Activity. A lot of ionic compounds are used in everyday lives. The table below shows some useful ionic compounds.


Table 7.4. Some useful ionic compounds.

Chemical Formula

Uses Chemical Name

CaCO3 Also known as limestone, component of cement and corals

calcium carbonate

KNO3 Used in explosives and matches potassium nitrate

NaHCO3 Used as baking ingredients sodium bicarbonate

NaF Cleansing agent, ingredient in toothpastes

sodium fluoride

CaSO4 • 2H2O Also known as Plaster of Paris, used as cast to sculpt materials

calcium sulfate dihydrate

Key Points

● Ionic compounds are solid; they are hard and brittle. ● Ionic compounds have relatively high melting and boiling point. ● Most ionic compounds are soluble with water. ● They are poor conductors when solid but good conductors in the molten

state and liquid state.

Web Links


● What is the science behind dissolved ions in gatorade and sports drinks? Watch it here: Reactions. 2017. ‘What do Electrolytes Actually Do?’ https://www.youtube.com/watch?v=xhLHtuZ3VOI


https://www.youtube.com/watch?v=xhLHtuZ3VOI

https://www.youtube.com/watch?v=xhLHtuZ3VOI

● What are the foods rich in several ions needed by our body? Check the list here: 7ReMix Healthy Tips TV. 2017. ‘Foods Rich with Electrolytes Naturally | Top 10 Electrolyte Replenishes Foods.’ https://www.youtube.com/watch?v=uFRpTA9qBZM


A. Write true if the following statements are correct. Write false if otherwise.

1. There are ionic compounds in the liquid form. 2. Ionic compounds have a very low melting point. 3. Ionic compounds conduct electricity at the molten state only. 4. Sodium chloride in solid state will not conduct electricity. 5. Sodium chloride dissolved in water will conduct electricity.

B. Fill in the table below by writing the name and formula of the compound which

will be formed by combining the anion and cation. Then, research in the internet for applications of these ionic compounds.

Fe3+ K+ Ba2+ Cu2+

Cl-

NO3-

SO42-

Challenge Yourself

1. Explain why ionic compounds are brittle. 2. Can a household vinegar or suka light up an LED bulb? How about a tablet of

vitamin C dissolved in water? 3. Is an ionic compound formed when any transition metal is combined with

oxygen?


https://www.youtube.com/watch?v=uFRpTA9qBZM

https://www.youtube.com/watch?v=uFRpTA9qBZM

4. The introductory photo in this unit shows that NaCl exists as a crystal rather than a single molecule with one cation and one anion. Why is this so? Explain briefly.

5. Is the potential energy diagram for bonding discussed in the previous section still applies for ionic bond? Is there still a specific distance for bonding to happen, or are closer distances better for ionic compounds?

Laboratory Activity

Activity 1 Properties of Ionic Compounds

Objective At the end of this laboratory activity, the students should be able to:

● observe properties of household ionic compounds Materials and Equipment

● vinegar (acetic acid), 10 mL ● baking soda (sodium bicarbonate), 1 g ● caustic soda (sodium hydroxide), 1 g ● table salt (sodium chloride),1 g ● distilled water ● improvised conductivity set-up

○ battery power pack ○ flashlight bulb ○ 3 pieces, insulated wire, at least six (6) inches in length ○ rubber bands ○ masking tape ○ wire stripper

● metal spoon ● alcohol burner ● vial, small container, or beaker ● medicine dropper

Procedure


Melting point test 1. Place a pinch of baking soda, caustic soda and table salt in a metal spoon. 2. Heat it for two minutes 3. Record your observation on the table below.

Solubility test

1. Place a pinch of baking soda, caustic soda and table salt in a small vial, container or beaker.

2. Add 3 mL of distilled water in each sample using the medicine dropper. 3. Record your observation on the table below.

Preparing an improvised electrical conductivity set-up

1. Remove at least an inch of coating in both ends of the 6-inch wires. 2. Wrap one end of each wires on opposite sides of the flashlight bulb. 3. On one side, wrap the exposed end to the positive side of the battery. 4. Using the last wire, wrap one end to the negative side of the battery. 5. The conductivity set-up is ready to use. You can fix portions of the loose ends

on a flat surface with masking tape. Electrical conductivity test

1. Place a pinch of baking soda, caustic soda and table salt in a small vial, container or beaker.

2. Test the conductivity of each solid by letting the loose ends of the conductivity set-up touch the samples.

3. Record your observation on the table below. 4. Dissolve the solids in 3 mL of distilled water. Then, test again the conductivity

of the solution by immersing the loose ends of the conductivity set-up into the solution.

5. Record your observation on the table below. 6. Similarly, test the conductivity of acetic acid by transferring 3 mL of it in a

container and immersing the loose ends of the conductivity set-up. Record your observation on the table below.

Waste Disposal Dispose solids in a regular trash bin. Dispose all solutions in sink with excessive amount of running water.

Data and Results


Record your observations below.

Table 1. Properties of household ionic compounds.

Household material

Melting Point Test

Solubility Test

Electrical Conductivity Test (Solid)

Electrical Conductivity

Test (Solution)

Baking soda

Caustic soda

Table salt

Vinegar

Guide Questions

1. Did the compounds melt easily? Why or why not? 2. Which compounds dissolved in water? Explain why did they dissolve in water. 3. Did the compounds conduct electricity in solid form? Why or why not? 4. Which compounds conduct electricity when dissolved in water? Why or why

not? 5. Which compounds are classified as ionic? Which are not? Explain briefly.

Performance Task

Sweet Cravings: Give Me Some Sugar! Your chemistry teacher is also a famous pastry chef in your community. She gave you five different solids labelled A to E. To you, they all look alike. They are white, crystalline solids. But your teacher told you that they may be bleach (sodium hypochlorite), vitamin c (ascorbic acid), washing soda (sodium carbonate), chalk (calcium carbonate) and the secret ingredient to her mouth-watering special chocolate cake - sugar. She asked you to identify which among the solids is sugar.


Goal ● Your task is to design a method in identifying which of the following solids is

sugar. ● The problem/challenge is how will you be able to devise a method despite

unavailability of chemical reagents and advanced technology in your school laboratory.

Role

● You are a brilliant student who excels in solving problems in chemistry. Audience

● Your audience is your Chemistry teacher. Situation

● You know the identities of the five solids. They may be one of the following: bleach (sodium hypochlorite), vitamin c (ascorbic acid), washing soda (sodium carbonate), chalk (calcium carbonate) and sugar.

● You know that all except sugar are ionic compounds. Product/Performance and Purpose

● You will conduct a series of experiment to be able to find out which solid is sugar.

● You will create a written report based on the results of the experiment. ● You will explain your methods and how did you arrive to the conclusion on

which of the following solids is your teacher’s secret ingredient. Standards and Criteria for Success

● Your work must meet the standards found in the rubric below. Rubrics for Assessment

Criteria Below Expectations 0% to 49%

Needs Improvement 50% to 74%

Successful Performance 75 to 99%

Exemplary Performance 100%

Comprehensiveness Methods does not justify the objectives

Shows some comprehensiveness, but most

Comprehensive, some methods meet the

Very comprehensive, method carefully


methods are not in line with the objectives

objectives but are not planned well

planned out and techniques meet the objectives

Reliability Methods produced no data

Shows some reliability, data can be gathered but cannot be analyzed further

Reliable, data gathering and analysis offers reliable results but sometimes show inconsistencies

Very reliable, data gathering and analysis offer highly reliable results

Innovativeness Does not exhibit effort to be original

Shows some originality, inadequate used of resources

Original ideas, adequate use of resources

Very original, shows imaginative use of resources

Self Check

Check I can…

Explain the meaning of an ionic bond

Explain how ions are formed

Write chemical names and chemical formulas of binary ionic compounds, ternary ionic compounds and hydrates

Recognize and explain properties of ionic compounds

Reflect


I find __________________________ the most interesting because ______________________. I got ____ checks because _______________________________________________________. I need to improve on _______________________because _____________________________. I need to practice _________________________ because _____________________________. I plan to _____________________________________________________________________ .

Key Words

Ion It is an electrically-charged atom.

Cation It is an ion that is positively-charged.

Anion It is an ion that is negatively-charged.

Isoelectronic Atoms or ions are isoelectronic if they have the same electron configuration.

Ionic bond It is the force which holds together cation and anion in a compound

Crisscross formula It is used to determine the final formula of the compound. The charge of the cation becomes the subscript of the anion, while the charge of the anion becomes the subscript of the cation.

Polyatomic cation It is a group containing two or more elements with a positive charge.

Polyatomic anion It is a group containing two or more elements with a negative charge.

Binary ionic compound

It is an ionic compound consists of one metal and one nonmetal.

Oxyanion It is an anion containing oxygen.


Oxyacid It is an oxygen containing acid.

Hydrates These are compounds which have a specific number of water molecules attached to a given compound.

Wrap Up

Formation of Ionic compounds

Photo Credits

Unit photo. Sodium chloride crystals (Halite 2) by Parent Géry is licensed under CC BY-SA 3.0 via Wikimedia Commons. Figure 10. Salt shaker on white background by Dubravko Sorić SoraZG is licensed under CC BY 2.0 on Flickr.


https://commons.wikimedia.org/wiki/File:Halite_2.jpg

https://commons.wikimedia.org/wiki/User:Parent_G%C3%A9ry

https://creativecommons.org/licenses/by-sa/3.0/legalcode

https://creativecommons.org/licenses/by-sa/3.0/legalcode

http://commons.wikimedia.org/

References

Brown, Theodore L. 2004. Chemistry: The Central Science (11th ed). Singapore:

Pearson Education (Asia) Pte Ltd.

Chang, Raymond. 2010. Chemistry (10th ed). New York: McGraw-Hill.

Padolina, Ma. Cristina D, et al. 2004. Conceptual and Functional Chemistry: Modular Approach. Philippines: Vibal Publishing House, Inc. .

Pavico, Ma. Josefina F. 2013. Exploring Life through Science: The New Grade 7. Philippines: Phoenix Publishing House, Inc. .

Silberberg, Martin S. 2009. Chemistry: The Molecular Nature of Matter and Change (5th ed). New York: McGraw-Hill.


unit 7 ionic bonding

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