How To Name Chemical Formulas

Supplemental to Chapter 20

Rules for Naming Binary Compounds

Binary Compounds are ionic bonds between one metal (+) and one nonmetal (-).

When you name binary ionic compounds, you always mention the cation (+ ion) first (usually the metal).

When you name the second ion (the – anion), you will change the ending to “ide”

Common Binary Anions

Oxygen oxide

Phosphorus phosphide

Nitrogen nitride

Sulfur sulfide

Chlorine chloride

Name These Binary Compounds

RbCl =

NaF =

CuO =

AlN=

K2S =

NaCl =

Name These Binary Compounds

RbCl = Rubidium Chloride

NaF = Sodium Fluoride

CuO = Copper Oxide

AlN= Aluminum Nitride

K2S = Potassium Sulfide

NaCl = Sodium Chloride

Polyatomic Ions

Polyatomic ions are a group of ions (2+ elements) that are covalently bonded together.

1) You would say the first element as is.

2) You would then say the rest of the bonded polyatomic ions after the first element, using their specific endings.

Polyatomic Ion Endings

Ammonium NH4

Acetate C2H3O2

Chlorate ClO3

Hydroxide OH

Nitrate NO3

Carbonate CO3

Sulfite SO3

Sulfate SO4

Phosphate PO4

Peroxide O2

Oxygen vs Peroxide

Normally an Oxygen molecule by itself is O2. However, if it is in a polyatomic bond, the O2 becomes peroxide.

O2 = oxygen, Na2O2 = sodium peroxide

Remember the difference between the chemical formulas for water and hydrogen peroxide: water = H2O; hydrogen peroxide = H2O2

Rules for Polyatomic Ions

• You have to memorize the chart, including SO3

(Sulfite) and O2 (Peroxide).

Remember, O2 is peroxide only when used as a polyatomic ion. Otherwise it is oxygen (oxide.)

Naming Polyatomic Ions

HSO4 -

NaNO3 -

Ba(OH)2 -

KNO3 -

CaCO3 -

CuSO3 –

CaSO4 –

(notice the different endings of the last two polyatomic ions.)

Naming Polyatomic Ions

HSO4 - Hydrogen Sulfate

NaNO3 - Sodium Nitrate

Ba(OH)2 - Barium hydroxide

KNO3 - potassium nitrate

CaCO3 - calcium carbonate

CuSO3 – copper sulfite

CaSO4 – calcium sulfate

H2O2 – hydrogen peroxide

Prefixes for Covalent Compounds

The prefixes indicate how many atoms of each element are in a binary covalent compound. These occur when 2 nonmetals covalently bond.

Prefixes for Covalent Compounds

Mono = 1

Di = 2

Tri = 3

Tetra = 4

Penta = 5

Hexa = 6

Hepta = 7

Octa = 8

How to Say Covalent Compounds

P2O5 - this is named diphosphorus

pentoxide, because there are two phosphorus atoms and five oxygen atoms.   CO - this is carbon monoxide (you need the "mono-" because there's only one oxygen atom). CF4 - this is carbon tetrafluoride

The Covalent Bond of Water

• Water is a covalent bond (2 Hydrogen atoms share the 6 Oxygen valence electrons of one atom)

H2O

Dihydrogen monoxide

This is a chemical formula you should know.

Naming Covalent Bonds Rules

• Use specific prefixes to indicate the total number of atoms involved.

• Don’t write 2 vowels together unless it is dioxide. (CO2 = carbon dioxide)

• If there is only one atom for both elements, you don’t write the “mono” for the first element, but you do for the 2nd element.

Examples: CO = carbon monoxide