Chapter 9Chemical Names and Formulas

Mr. RobertsChemistry Level 2

Section 1 – Naming Cations

Group A Elements• Just write name of metal and add “ion” to

ending• Example:

– Na+1 sodium ion– Al+3 aluminum ion

Naming Cations

Group B Elements (transition metals)• Ionic charge will change so write Roman

Numerals in parenthesis after name of metal to indicate charge. (Stock System) – Table 9.2 page 255

Naming Cations• Some post transition element also have charges

that will change.– Ex: Tin and Lead

• Sn+2 Sn+4

• Pb+2 Pb+4

• Some transition metals only have one ionic charge. Therefore you don’t use roman numerals.– Silver Ag+1

– Cadmium Cd+2

– Zinc Zn+2

Naming Anions

• Always have the same charge!– Change suffix with - ide– Ex: F-1 Fluoride ion

O-2 Oxide ion

Polyatomic Ions

• Group of atoms that stay together and have an overall charge

• Usually end with –ate or –ite (one less oxygen)• Ex: (SO3)-2 Sulfite

(SO4)-2 Sulfate

(NH4)+1 ammonium

Section 2 – Writing/Naming Ionic Compounds

Finding the formulas for ionic compounds.• Criss-Cross Method

• Remember…ionic compounds must be expressed in the lowest whole number ratio.

Lose sign

value

Naming Ionic Compounds

• Binary Ionic Compounds (2 ions)– Use rules for naming ions– Ex: Na+1Cl-1 {sodium ion and chloride ion}

NaClSodium Chloride

Naming Ionic Compounds (continued)

• Naming Ternary Ionic Compounds (involving a polyatomic ion group)

• Name it as it appears• Ex: CaCO3 calcium carbonate

Mg3(PO4)2 magnesium phosphate

CaSO4 calcium sulfate• If ammonium or any other polyatomic cation is

reacting with a monatomic anion use binary ionic rules

Naming Group B Ionic Compounds• Rules for naming binary and ternary ionic

compounds apply• Include a roman numeral in parenthesis to

indicate the ionic charge.– Use the reverse of the criss cross method to

determine the charge.– Ex:

Section 3 – Molecular CompoundsNaming Binary molecular compounds (2 nonmetals)• Name the elements in order they appear.• Drop ending of second element and replace with

suffix “ide”.• Use prefixes to indicate # of atoms present

– Table 9.4 page 269

Binary Molecular CompoundsMono = 1Di = 2Tri = 3Tetra = 4Penta = 5Hexa = 6Hepta = 7Octa = 8Nona = 9Deca = 10

Examples:

N2O dinitrogen monoxide

CO2 carbon dioxide

CO carbon monoxideSF6 sulfur hexafluoride

9.4 Naming and Writing Acids• Acid: a compound contain H+ ions.

Anion Ending

Acid Name with Suffix

Acid Ending

Example

- ide hydro________ic acid HCl – hydrochloric acid

- ite ____________ous acid H2SO3 – sulfurous acid

- ate _____________ic acid H2SO4 – sulfuric acid

Examples

HF

HClO2

HClO3

Hydrofluoric Acid

Chlorous Acid

Chloric Acid

Naming and Writing Bases

• Base: a compound containing OH-1

• Named in the same way as other ionic compounds

• Example: NaOH sodium hydroxide

Section 9.5 – The Laws Governing Formulas and Names

We are able to name compounds and write their formulas because they form from elements in

predictable ways

1. The Law of Definite Proportions

• In samples of any chemical compound, the masses of the elements are always in the same proportions.

2. The Law of Multiple Proportions

• Whenever the same two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.– John Dalton