chemistry second 9 weeks. class today midterm is on wednesday chemistry website:...

ChemistrySecond 9 weeks

Class Today• Midterm is on Wednesday• Chemistry Website: hcchemistry.wikispaces.com• Tutoring on M-W make appt• Calendar has plans for remainder of semester• Can go ahead and complete WS ahead of time, • Can check Power point lectures for quizzes and

homework to complete ahead of time.• Charges and Ions WS• Ionic Compounds I Power point and Skeleton Notes

Website for Chemistry

• http://hcchemistry.wikispaces.com/ • Study at home every night• Complete homework (homework check)• Participate in class (note check)• Books taken home (red flag!) • Those doing the above that still need help, see

me about tutoring on M, T, W from 3:30 to 4:30…arrange ahead of time as I sometimes have meetings scheduled.

Midterm

• Study Guide suggests concepts to be sure to know.

• Refresh by reading textbook. • Study class notes. • Website has previous power point lectures

and handouts. • Wednesday October 13th MIDTERM

Compounds

• Law of Constant Composition: All samples of a given compound have the same proportions of their constituent elements

• Every molecule of water has H2O, every molecule of sugar is C6H12O6

What does a formula mean?

H is the symbol for ?

O is the symbol for ?

2 is how many Hs there are

How many Os?

More complicated…

• Mg(NO3)2

• There is one Mg• There are 2 groups of (NO3)

• In each NO3 there is 1 N and 3 O

• The math 2 * 1N = 2N • The math 2 * 3O = 6O• Total # of atoms is = 1 Mg 2 N 6 O• But never change the subscripts!

2 Compound Types

• Ionic Compounds: Are between two or more ions, most of them are between a metal and a non-metal

• Molecular Compounds: Are between 2 or more non-metals

Compound TypesIonic: Metal and a non-metalMolecular: 2 non metals

Oxidation States

• Elements in compounds have oxidation states• Oxidation State determines the behavior of

the element when it is near other elements.• Some elements have only one oxidation state,

others have several

Memorize this Table

• OXIDATION NUMBERS• Group 1= +1• Group 2= +2• Group 13= +3• Group 15= -3• Group 16 = -2• Group 17= -1• Group 18 = No Charge Ever!

Ionic Compounds

• Metal (left side of the stair step) lose electrons to minimize electron-electron repulsion or to eliminate their valence electrons entirely.

• Nonmetals tend to gain electrons to acquire an octet of electrons.

• Octet = 8 valence electrons (ns2np6) where n is the highest energy level occupied.

Ionic Compounds

• Transition metals have an oxidation state or number = +2

• Noble gases – unreactive because they have an octet already

Ionic Compounds

• Sulfur, S, has a valence electron configuration of 3s23p4 (6 valence electrons)

The oxidation number for S is –2 so Sulfur will form S-2 ions.

S-2 has 8 valence electrons 3s23p6 and is more stable with an octet. It mimics Argon (a noble gas)

How are atoms in Ionic Compounds held together?

• By chemical bonds formed by the attraction of oppositely charged ions.

How do atoms become ions?

• Ions are formed whrn atoms gain or lose valence electrons to achieve a stable electron configuration….an octet of 8 valence electrons.

Ionic Compounds

• Oppositely charged ions attract each other.• The Ionic Compound is overall neutral, but

each component ion has a charge. So, we have to make sure that charges are balanced.

Create a Foldable

Ion Formation Ionic Bonds Properties of Ionic

Compounds

Create a Foldable

Ion Formation Ionic Bonds Properties of Ionic

Compounds

Read Section 7.1 and 7.2 and record information about ionic compounds in the appropriate column on the foldable. This will be turned in or checked for completion and participation.

Section 7.1• Ions are formed when atoms gain or lose

valence electrons to achieve a stable octet electron configuration (that of the closest noble gas).

• Elements in the same group have similar properties. These properties are related to the # number of valence electrons.

Section 7.1• Valence electrons are involved in the

formation of chemical bonds between 2 atoms

• A chemical bond is the force that holds 2 atoms together.

Chemical Bonds• Can be formed by the attraction between the

positive nucleus of one atom and the negative electrons of another atom. (I.e attraction between positive and negative ions.)

• Can be formed by the sharing of electrons between atoms. (Ch. 8…later)

Electron Dot Structures

• Keeps track of the valence electrons

• Elements tend to react to acquire the stable electron structure of a noble gas

Positive Ions• When an atom loses 1 or more valence

electrons in order to achieve a noble gas configuration.

• Called a CATION• 1s22s22p6 is noble gas Neon• 1s22s22p63s1 is a Sodium atom• 1s22s22p6 = Na+1

• The Sodium cation is NOT Neon as it still has 11 protons in its nucleus

Metals Lose Electrons• Metals lose valence electrons easily and are

therefore reactive• Transition metal ions will lose their 2 s orbital

valence electrons to become +2 ions.• Sometimes one of the inner d electrons will

also be lost and the metal becomes a +3 ion.

Negative Ions• Nonmetals (right side of periodic table) gain

electrons to get a stable outer electron configuration of the closest noble gas.

• Chlorine gains an electron to achieve noble gas configuration and forms a –1 ion.

• Chlorine is 1s22s22p63s2 3p5

• Argon is 1s22s22p63s2 3p6

• Cl-1 is 1s22s22p63s2 3p6

Negative Ions• Are called ANIONS• An Anion is a negatively charged ion. • To designate an anion, the ending is changed

to –ide. Chloride ion.• Group 15 becomes –3 anions• Group 16 becomes –2 anions.• Group 17 becomes –1 anions.

Negative Ions• P has 5 valence electrons• P-3 has 8 valence electrons = phosphide ion• O has 6 valence electrons• O-2 has 8 valence electrons = oxide ion

QUIZ1) Compare the stability of a lithium atom with that of

an ion, Li+1

2) Why are elements in Group 18 unreactive, while those in Group 17 are very reactive?

3) Summarize how ions are formed using the terms: electron gain, electron loss, anion and cation.

4) Write e- configurations for each atom and then e- configurations for the change that happens for each to achieve noble gas stability. N, S, Li, Ba

5) Draw an illustration showing the formation of a positive Calcium ion and a negative Bromide ion.

SUMMARY• A chemical bond is the force that holds two

atoms together.• Some atoms form ions to gain stability.• A stable electron configuration involves a full

energy level, usually 8 electrons.• Ions are formed by the loss or gain of valence

electrons.• The number of protons remains unchaged

during ion formation

Homework for Ch. 7.2

• P. 217 12-17

Ionic Bonds and Ionic Compounds

• Oppositely charged ions attract each other forming neutral ionic compounds.

• Formation of Ionic Bonds occurs in the following:

• Magnesium burning • Reaction of Na and Cl to make NaCl.

• In the videos, elements are reacting to form compounds.

• What was the indication that a chemical reaction was taking place?

• In Sodium metal and Chlorine gas. The Na atom transfers its outer electron to the Cl atom. Na+ and Cl accepts and becomes Cl-

• The Na+ and Cl- are attracted and the compound sodium chloride NaCl is made.

Ionic Bond• The electrostatic force that holds oppositely

charged particles together in a compound.

Ionic Compounds• Compounds that contain ionic bonds.• Metal + oxygen = an oxide (Mg and O)• Metal + Nonmetal = “salt” (Na and Cl)

Binary Ionic Compound• Contains 2 elements .• Metal cation and Nonmetal anion

Calcium Fluorine

[Ar] 4s2

Wants to lose 2 e-lose 2 e- to become like Argon

[He] 2s2 2p5

Wants to gain 1 e-gain 1 e- to become like Neon

Ca+2 F-1

The charge that is on the ions is given by oxidation #

Calcium Fluorine

Ca+2 F-1

The charge that is on the ions is given by oxidation #

Calcium Fluorine

Ca+2 F-1

When these two elements are together, electrons are transferred and ions created. The ions then have an electrostatic attraction and an ionic compound is made.

Ca F

F

CaF2

Ionic Compound Making

• 1- Write their symbols• 2- Write their charges to the upper right• 3- Crossover• 4- (Reduce to lowest ratio)• MEMORIZE THIS!

Ca+2 F-1= CaF2

Ionic Compound Example 1

• Magnesium and Chlorine form a compound what is the formula?

• Mg Cl• Mg+2 Cl-1 crossover

• Mg1Cl2 can also write this as MgCl2

• 1:2 does not reduce any further

Ionic Compound Example 2

• Aluminum and Chlorine form a compound what is the formula?

• Al Cl• Al+3 Cl-1 crossover

• Al1Cl3 can also write this as AlCl3

• 1:3 does not reduce any further

Ionic Compound Example 3

• Aluminum and Oxygen form a compound what is the formula?

• Al O• Al+3 O-2 crossover

• Al3O2

• 3:2 does not reduce any further

Ionic Compound Example 4

• Magnesium and Oxygen form a compound what is the formula?

• Mg O• Mg+2 O-2 crossover

• Mg2O2

• 2:2 does reduce to 1:1• Mg1O1 or MgO

Ionic Compound Example 5

• Aluminum and Nitrogen form a compound what is the formula?

• Al N• Al+3 N-3 crossover

• Al3N3

• 3:3 does reduce to 1:1• Al1N1 or AlN

QUIZ on writing Ionic Formulas

1) Explain how an ionic compound forms from Lithium (Li) and oxygen (O).

2) What is the final formula?3) Explain how an ionic compound forms from

sodium (Na) and Nitrogen (N).4) What is the final formula?5) Explain how an ionic compound forms from

Aluminum and Sulfur.6) What is the final formula?

Naming Ionic Compounds

• Ionic Compounds are between metals and non-metals

Naming Metals

• Alkali (Group 1) , alkaline earth (Group 2), and group 3 metals are easy to name in compounds……Just use what you see on the periodic table.

• Al is aluminum, Na is sodium, Mg is Magnesium

Transition Metals

• Alkali metals are easy. The charge is always +1. Alkaline earth metals are easy the charge is always +2. Group 13 metals are easy the charge is always +3.

• Transition metals, lanthanides, actinides, and all the other metals are trickiertrickier. There are multiple charges they can have and multiple names for the metals depending on their charge.

T.M. Example

• Iron can exist in stable forms with a +2 or +3 charge. We write the symbol as as Fe+2 and Fe+3 or Fe(II) and Fe(III) or Iron (II) and Iron (III)

• Copper typically has a +1 or +2 charge. We will write it as Cu+1 or Cu+2 or Cu(I) and Cu (II) or Copper (I) and Copper (II)

Transition Metals

• Chemistry is old. We’ve actually gone through 2 naming systems for transition metals.

• The old system had certain names for certain charges. Fe+2 and Fe+3 were called ferrous and ferric. We won’t use those names now, but you should be familiar that you might see this old naming system at times.

Naming Ionic Compounds

• The non-metal in ionic compounds gets it’s name changed.

• Chlorine becomes chloride• Oxygen becomes oxide• Nitrogen becomes nitride• Fluorine becomes Fluoride• Sulfur becomes Sulfide• Iodine becomes Iodide

Formula AND Naming Ionic Compounds

• Magnesium and Nitrogen form a compound what is it’s formula and name?

• Mg N• Mg+2 N-3

• Mg3N2

• Can’t reduce further• Magnesium Nitride (easy as Mg is a Group 2

metal so just say its name)

What about Iron (II) and Nitrogen

• Fe and N• Fe+2 and N-3

• Fe3N2

• 3:2 doesn’t reduce• Iron (II) Nitride

It’s a lot to learn

• Chemistry is a lot to learn.• Most of you had this material last year in ICP• You will not learn new Chemistry material by

just “being” in class. • You will need to complete homework• You will need to take notes in class.• You will need to take your book home each

night and study.