Chemical Formula and Naming

Octet rule: atoms react to acquire a full outer shell:

• Give away an e- to another atom.• Take an e- from another atom.• Share an e- with another atom.

Ionic bond

Covalent bond

An ION is an atom that has lost or gained an electron.

Lose e- – positive ion OR cation. (metals)Gain e- – negative ion OR anion. (nonmetals)

Writing Rule 1: Write the symbol of the metallic element first.

Be Cl

Rule 2:

Place the combining capacity of one element as a subscript of the other element.

Beryllium combines with Chlorine

+ -12

Rule 3: Leave subscripts with a value of 1 out.

Be Cl2 1

Two Naming rules: 1. Write the full name of the metal ion first. 2. Name the non-metal ion dropping the last part of the name and adding the suffix “ide”.

berylliumchloride

Rule 4: Reduce the subscripts if possible.

Mg S

Magnesium combines with Sulfur

Mg S + -22

magnesium sulphide

Transition metals can give away different numbers of electrons.

To avoid confusion:

Brackets are used to show how many electrons the Transition metal is giving away.

Iron (III) chlorideIron (II) chloride

Fe Cl + -12

FeCl2

Fe Cl + -13

FeCl3

Write the name of the ionic compound:

PbO

Pb O+ -1

2

lead oxide(IV)

+4 -2

Covalent Compound:

Contain two or more NON-METAL atoms.

Formed by SHARING valence electrons to fill outer shell – octet rule.

· A molecule is the smallest unit of a covalent compound.

Non-metal + Non-metal = covalent bonding

Prefix Number of Atoms

mono 1di 2tri 3

tetra 4penta 5hexa 6hepta 7octa 8nona 9deca 10

Step 1: first non-metal is named with a prefix to show the number of atoms.

We do not use “mono” for the first non-metal.

nitrogen oxide

N O

Step 2: second non-metal is named with a prefix AND with the “ide” ending.

di

2 4

tetradinitrogen tetroxide

PrefixNumber of

Atoms

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6

Writing formulas

Step 1: Write the symbol of each element.

Step 2: Use a subscript to show the number of each type of atom given by the prefix.

Do not reduce covalent formulas.

phosphorus oxide

P O di

2 5

penta

PrefixNumber of

Atoms

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6

Polyatomic Ions (poly = many)

Groups of covalently bonded atoms that act as ions.

Polyatomic ions function as one unit with one charge – lose or gain electrons.

DO NOT change the subscripts of polyatomic ions.

Al(C2H3O2)3

Write the name of the ionic compound:

Al(C2H3O2)

Al C2H3O2

+ - 1

3

aluminum acetate

nickel (II) nitrate

MgSO4

potassium permanganate

Fe(OH)3

calcium acetate

Ag2CrO4

lead (II) carbonate

Sn(SO4)2

sodium hydrogen phosphate

NH4NO2

1. Ni(NO3)2

2. magnesium sulfate

3. KMnO4

4. iron (III) hydroxide

5. Ca(C2H3O2)2

6. silver chromate

7. PbCO3

8. tin (IV) sulfate

9. Na2HPO4

10.ammonium nitrite