Chemical Names and Formulas

Monatomic IonsCations

• Groups 1A, 2A, 3A charges = group number• Name: element name “ion”• Examples:• Na+ sodium ion• Mg2+ magnesium ion• Al3+ aluminum ion

Common Cations

Monatomic IonsAnions

• Group A element charges = 8 - group number• Name: stem of element name + ide• Examples– Cl- chloride– S2- sulfide– O2- oxide– N3- nitride

Monatomic IonsTransition Metals (Group B)

• Charges can’t be predicted from Periodic Table• Some are “multivalent”

– Form more than one ion• Name: element name (charge) “ion”• “Stock” naming system

– Use Roman numerals to indicate charge• Examples: Stock name Classical name• Fe2+ iron (II) ion ferrous ion• Fe3+ iron (III) ion ferric ion• Cu+ copper (I) ioncuprous ion• Cu 2+ copper (II) ion cupric ion

Ionic Charges of Representative Elements

Multivalent Cations

Polyatomic Ions

• Group of covalently bonded atoms that has a net charge

• Most are anions• Oxyanions contain oxygen– End in –ate or –ite– SO4

2- sulfate SO32- sulfite

– NO3- nitrate NO2- nitrite

Common Anions

Chloroxyanions

• Polyatomic ions containing oxygen and chlorine

Formula Name

ClO- hypochlorite

ClO2- chlorite

ClO3- chlorate

ClO4- perchlorate

Polyatomic Ions

• Some begin with hydrogen

• H+ + CO32- → HCO3

- hydrogen carbonate

• H+ + PO43- → HPO4

2- hydrogen phosphate

• H+ + HPO42- → H2PO4

- dihydrogen phosphate

Polyatomic Cations

• Only 2• Ammonium Ion NH4

+

• H+ + :NH3 → NH4 +

• Hydronium Ion H3O+

• H+ + H2O: → H3O+

9.3 Naming and Writing Formulas for Molecular Compounds

• Molecular compounds are named using a system of prefixes to indicate the number of each element in the compound

• Do not use mono- before the first element• Example: SF6 sulfur hexafluoride• Example N2O4 dinitrogen tetroxide

9.4 Formulas and Names of Acids & Bases• Acids are compounds that have one or more

ionizable hydrogens• General formula HnX• HCl (g) + H2O → H3O+ + Cl- (aq)

Common Acids

Names & Formulas for Bases

• Bases are compounds which produce the hydroxide ion when dissolved in water

• NaOH (s) → Na+ (aq) + OH- (aq)• NH3(g) + H2O → NH4

+ (aq) + OH- (aq+

• Name as you would ionic compounds

Law of Definite Proportions• aka Law of Constant Composition• For any compound, the percent composition by

mass is always the same• A given compound always contains elements in

exactly the same proportion by mass• E.g. percent composition of water by mass is

11.1% H and 88.9% O regardless of how much or how little there is

• An ice cube and an iceberg have the same % composition.

Law of Multiple Proportions• When two elements form different

compounds, the mass of one element combining with the same mass of the other element occur in small whole number ratios

H2O2 H2O

Mass O 32 g 16 g

Mass H 2 g 2 g

Ratio O:H 16:1 8:1

Ratio O:O 16:8 = 2:1

Flow Chart to Name Chemical Compounds