Nomenclature

Chapter 8

CP Chemistry

Spring 2013

Ionic Compounds• Atoms held together by

ionic bonds.• What are ionic bonds?

– Between metals and non-metals– Transfer of electrons

between atoms.– Attraction between

oppositely charged ions.

Ionic Compounds• Some examples are:

– MgCl2– MgCl2– KBr– Li2O

• These are all bonds between cations (positive ions) and anions (negative ions).

Naming Ionic Compounds• Binary Ionic Compounds

– The metal will be your cation. Its name comes first.

– The non-metal will be your anion. Its name comes second, but undergoes a slight change.• Change the ending to –ide. • Example: Chlorine Chloride, Nitrogen Nitride

•Li2O Lithium + Oxygen

Metal Non-Metal

ide

Practice

• Name the following ionic compounds:

– MgCl2– Rb2S

– BeF2

– Cs3N– KI– In ionic compounds, the subscripts do NOT

affect the name of the compound.

magnesium

Chlorineide

Rubidium Sulfide

Beryllium Fluoride

Cesium NitridePotassium Iodide

• Polyatomic Ions– Ions made of multiple atoms.– Name using an ion chart, but otherwise

name the same as binary compounds.– Examples:– MgCO3 = Magnesium Carbonate

– (NH4)2SO4 = Ammonium Sulfate

Writing Formulas from Names• The key to writing correct ionic

formulas is to balance your positive and negative charges. We want a neutral molecule.

• The “crossover method” is one strategy:

The charge of the cation (metal ion) becomes the subscript of the anion.

The charge of the anion (non-metal ion) becomes the subscript of the cation.

Writing Formulas From Names• Sodium Chloride

• Sodium = Na+, Chlorine = Cl-

Na1Cl1

NaCl

Writing Formulas from Names• Magnesium Fluoride

• Magnesium = Mg2+, Fluorine = F-

Mg1F2

MgF2

**Do not include the charge in your formula.

Why does this work?• Magnesium Fluoride

2+

-1

-1

2 + -2 = 0

Magnesium Fluorine

Ionic Naming using Transition Metals (and Tin and Lead)

• The charges of transition metals can vary. SO use a ROMAN numeral to tell what the cation charge is. . .

• You can use the formula to determine its charge in a specific molecule.

• Writing Formulas From Names• You can write the formulas for ionic compounds

with transition metals the same way as ionic compounds using alkali or alkaline earth metals.

Mercury (I) SulfideMercury = Hg+1, Sulfur = S2-

Hg2S

Example #1• CuI2• We know Iodine has a charge of -1, but we have to

determine the charge of copper.

+?

-1

-1

Copper Iodine

____ + -2 = 0

So… the charge of Copper in this molecule must be +2.

The name is written:

Copper (II) Iodide

Example #2• Mn2Cl4

+?

-1

-1

-1

-1

+?

Manganese Chlorine

2 x ? + -4 = 0

We are trying to find the charge of one Manganese atom.

The charge of one Manganese atom is +2, so the formula for Mn2Cl4 is:

Manganese (II) Chloride

Practice

• NiS2

• AgF• Sn3N4

• Lead (III) Phosphide

• Titanium (IV) Chloride• Chromium (II) Iodide

Writing Formulas from Names• You can write the formulas for ionic compounds using transition

metals the same as ionic compounds using alkali or alkaline earth metals.

Mercury (I) Sulfide

Mercury = Hg+, Sulfur = S2-

Hg2S

Molecular Compounds• Held together by Covalent bonds.

– Between two or more non-metals.– Sharing of electrons

• Examples:– H2O

– C2H4

– SO

Naming Molecular Compounds

• Begin by writing the name as you would a binary ionic compound.

• Add prefixes to each name which tell you how many of that atom are in the molecule.– If there is only one

atom of the first element in the molecule you can leave out the “mono” prefix on the first element only.

Prefix Definitions

Mono = 1

Di = 2

Tri = 3

Tetra = 4

Penta = 5

Hexa = 6

Hepta = 7

Octa = 8

Nona = 9

Deca = 10

Practice

• P2S3

• H2O

• CO

• N2O4

Metal + Non-metal or presence of polyatomic

ion

2 non-metals (Carbon, Silicon, elements in

groups 15-17, or Hydrogen)

Includes Transition metal,

Lead or Tin

Name using prefixes. Charges are not

relevant.

Includes Alkali or

Alkaline Earth Metal

Must include charge of

transition metal in parentheses.

Name using binary ionic

rules. No charge in

parentheses needed.