the making of compounds. compounds compounds – the combination of two or more elements. have new...
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The Making of Compounds
Compounds
Compounds – The combination of two or more elements.
Have new chemical and physical properties…different from each element.
Most of the matter around us is in the form of compounds or mixtures of compounds.
Compounds
Ex: Sodium – shiny, soft, gray metal…reacts violently with water
Ex: Chlorine – greenish, yellow gas … can kill if in air.
The compound of Sodium and Chlorine make SALT.
Compounds
Made through CHEMICAL BONDS – attractive force that holds atoms together.
Chemical Formula – The chemical shorthand for a compound.– Includes the chemical symbols and the
number of atoms of that element.
Compounds The goal of every atom is to be
chemically stable…with 8 outer electrons. (Octet Rule)
An atom will form compounds to become stable.
An atom only uses its valence electrons to form compounds.
Can use Dot Diagrams to show the number of electrons in the outer shell.
Dot Diagrams and Compounds Ex: Water (H2O)
Hydrogen has one valence electron Oxygen has 6 valence electrons Neither are stable…Will form a
compound to become stable
Types of Chemical Bonds: Ionic Bonding Ionic Bonds –
The force of attraction between opposite charges of ions– Simple
definition: Atoms give up or take electrons to become stable.
Ionic Bonding Example Sodium has one valence
electron Chlorine has 7 valence
electrons Sodium gives up its 1
electron to Chlorine…They both become STABLE
Sodium becomes positive (gives up electron
Chlorine becomes negative (takes an electron)
Types of Chemical Bonds: Covalent Bonding Covalent Bond – A bond that forms
between atoms when they SHARE electrons
Covalent Bonds (example) CH4 is made with Carbon
and Hydrogen sharing electrons.
Carbon has 4 valence electrons
Hydrogen has 1 valence electron
Carbon bonds with 4 Hydrogen atoms to become stable…they SHARE electrons to make all parties happy
Oxidation Numbers
The number of electrons that an atom will give up or take.
Useful when making compounds. Oxidation numbers are known by the group
an element is in– Example Group 1 – Oxidation # +1– Group 2 - +2– (handout shows oxidation numbers)
Groups 3-12 have variable oxidation numbers…depends on the compound it is making.
Polyatomic Ions
An ion made of two or more atoms. These are groups of covalently bonded
atoms that have either lost or gained electrons. (combination of bonds)
Polyatomic Ions are often found together in nature…have own name and oxidation numbers.
Polyatomic Ions(p. 158)
Put the following on your periodic chart:
Ammonium
Carbonate
Chlorate
Hydroxide
Nitrate
Phosphate
Sulfate
Making Compounds…Names and Formulas Compound Formulas – made with the
chemical symbol and the number of atoms used
Example: H2O uses 2 Hydrogen atoms for every 1 Oxygen atom.
Example: H2SO4 uses 2 Hydrogen atoms to 1 Sulfate ion
Making Compounds
1. Find Chemical Symbols 2. Find Oxidation Number for that
Element 3. Write the Chemical Symbol with the
Oxidation Number as a Superscript– Example: Sodium and Chlorine– Na+1 Cl-1
Making Compounds 4. Criss-cross the oxidation numbers…(give
the number to the opposite element as a subscript)– Na+1 Cl-1
– To: Na-1 Cl+1
5. Drop the sign (+ / -)– Na1Cl1
6. Write the compound – NaCl (when the subscript is 1 it does not have
to be written)
Making CompoundsPractice Practice:
– 1. Calcium and Nitrogen– 2. Magnesium and Oxygen– 3. Calcium and Chlorine
Making CompoundsPractice Answers: 1. Calcium and Nitrogen
– Ca+2 Nitrogen-3
– Ca3N2
2. Magnesium and Oxygen– Mg+2 O-2
– Mg2O2 or MgO
3. Calcium and Chlorine– Ca+2 Cl-1
– CaCl2
Naming Compounds
Most of the time you can name an IONIC Compound by– 1. Writing the Name of the FIRST
ELEMENT– 2. Writing the ROOT of the SECOND
ELEMENT– 3. Adding –IDE to the root
Naming Compounds: Examples
CaCl2 - Calcium chloride
K3P - Potassium phosphide
Al2S3- Aluminum sulfide
Naming Compounds
Some of our metals have more than one ionic charge– 1. We have to figure out what the ionic
charge is– 2. Then we must show which of the
elements it is with a roman numeral
Naming Compounds: Examples
FeCl2 - Iron(II) chloride
FeCl3 - Iron(III) chloride
PbBr2 - Lead(II) bromide
Naming Compounds
If the compound has a polyatomic ion in it:– 1. Write the name of the FIRST element– 2. Then find the name of the
POLYATOMIC ION and write it
Naming Compounds:With Polyatomic Ions
Fe(OH)2 - Iron(II) hydroxide
Ca3(PO4)2 - Calcium phosphate
Na2SO4 - Sodium sulfate