Nomenclature: The

ABC’s of Naming

Chemical Compounds

Table of Contents

1.Naming Ionic Compounds Type I

2.Naming Ionic Compounds Type II

3.Naming Covalent Compounds

4.Naming Polyatomic Compounds

Welcome to your

“NEW”

Periodic Table• This periodic table identifies

several aspects of the

elements we already know.

• This IS a reference tool.

• This IS NOT a cheat sheet.

• You will only ever be

allowed to use ONE of your

periodic tables at a time.

Ionic CompoundsType I

Ionic Compounds Without Transition

MetalsIonic compounds are formed when a metal gives up its electrons to a non-metal. Basically if the

compound contains a metal, it is ionic. But there are different sets of rules for transition

metals. A transition metal is an element with an atomic number of 21 to 30, 39 to 48 or 57 to

80.

So for a compound with any other metal, apply these rules:

1. The metal ion's name does not change regardless of charge.

2. The non-metal's name ends in the suffix “-ide”.

For example: AlCl3 = aluminum chloride

Na2S = sodium sulfide

K2O = potassium oxide

MgH2 = magnesium hydride

Notice how the little numbers (subscripts) do not affect the way we name them. In going

backwards (from name to formula), we will have more fun. In such a case the total charge of

the (+) and (-) ions in the compound has to be ZERO.

Example: What is the correct chemical

formula for Calcium Phosphide?

Here, we have to consider the common charges for calcium and phosphorus,

which are +2 and -3, respectively. Calcium, if you recall, typically loses two

electrons to get a noble gas electron arrangement, and phosphorus needs three

more electrons.

Ca+2 and P-3

One of each would create a sum of 2 + (-3) = -1. To get a sum of zero, we need

three Ca+2 ions and two P-3 for a total of 3(2)+ 2(-3) = 0.

So the answer is Ca3P2.

Other examples: potassium oxide : K+1 and O-2 yields K2O

aluminum bromide: Al+3 and Br-1 yields AlBr3.

Kriss-Kross Method for determining

Chemical Formulas

P32

Ca

P3 2

Ca

• Using the Kriss-Kross Method helps us to determine the chemical formula for a

chemical compound when given a written equation.

• For example you have been given the compound Calcium Phosphide. Below you

will see an example of how to use this method to determine its formula.

P3-2+

CaStep 1: Write out the ion

forms of both elements.

Step 2: Take the

absolute value of the

charge and Kriss-Kross

their positions to the

opposite element.

Step 3: Write the

chemical equation in its

reduced form.

Ionic CompoundsType II

Ionic Compounds with Transition Metals

The only difference here is that we have to specify

the charge of the transition metal ion by using a

Roman numeral, and keep in mind that a transition

metal is an element with an atomic number of 21 to

30, 39 to 48 or 57 to 80.

The reason we do this is not for the sake of

nostalgia for bygone Roman numerals nor to imitate

movie credits. Because transition metals can assume

more than one charge, we have to specify which one

is involved

Example: manganese(II) oxide contains Mn+2 and O-2.

So we just need one of each and the formula

becomes MnO.

Copper(I) oxide is Cu2O.

To go backwards, we need to figure out the charge

of the transition metal.

Roman

NumeralNumber

I 1

II 2

III 3

IV 4

V 5

VI 6

VII 7

Covalent CompoundsType III

Naming Rules and Prefixes

Step 1: Name the 1st element with its name

Step 2: Name the 2nd element with the suffix “-ide”

Step 3: Use the prefixes to denote the number of atoms of each element.

Step 4: Do NOT use the “mono” prefix on the 1st element.

The only time we drop a prefix is if the mono is to appear at the

beginning of the name.

1 - mono

2 - di

3 - tri

4 - tetra

5 - penta

6 - hexa

7 - hepta

8 - octa

9 - nona

10 - deca

Naming Examples

Compound Formula: OCl2First Element: Oxygen

Second Element: dichloride

Compound Name: Oxygen

Dichloride

Compound Formula: PCl51st Element: Phophorus

2nd Element: pentachloride

Compound Name: Phosphorus

pentachloride

Check for Understanding

Name Compound FormulaUse the Nomenclature rules to determine the correct

names of the following compounds.

CO

CO2

CH4

Compound Formula NameUse the Nomenclature rules to determine the correct

compound formulas of the following compounds.

dinitrogen pentoxide

phosphorus trichloride

Dihydrogen monoxide

Polyatomic Compounds

Naming Polyatomic Compounds

When metals are bonded to polyatomic ions, which consist of two or more

atoms with one overall charge, the same rules apply, but you have to learn

the names and charges of common polyatomic ions.

Na2CO3 = sodium carbonate. ( This is a useful chemical in purifying others; it is

sometimes called washing soda)

KNO3 = potassium nitrate ( This is an ingredient of gunpowder and it is also found

in fertilizer.)

To go backwards: Aluminum sulfate

This has Al+3 and SO4-2. To get a sum charge of ZERO, we need two aluminum

ions and three sulfates, so the formula becomes Al2(SO4)3. Notice that when

there is more than one polyatomic group, we make use of brackets.

List of Polyatomic IonsWhile memorization of these are not required it would be a

good idea to know the ones with a star next to them.

Review Day

Nomenclature Summary

Use this chart to help determine the names of

chemical compounds

Does the compound contain a metal?

Is the metal a TRANSITION METAL?

Use I, II, III, IV, V to indicate the charge

of the metal

Don’t use roman numerals; Don’t use

prefixesCompound is COVALENT; Mono=1,

Di=2, Tri=3, Tetra=4, Penta=5

YES

YES

NO

NO