Chemical Names and Formulas

Monatomic Ions Cations Groups 1A, 2A, 3A charges = group number Name: element name “ion” Examples: Na + sodium ion Mg 2+ magnesium ion Al 3+ aluminum ion

Common Cations

Monatomic Ions Anions Group A element charges = 8 - group number Name: stem of element name + ide Examples – Cl - chloride – S 2- sulfide – O 2- oxide – N 3- nitride

Monatomic Ions Transition 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 nameClassical name Fe 2+ iron (II) ionferrous ion Fe 3+ iron (III) ionferric ion Cu + copper (I) ioncuprous ion Cu 2+ copper (II) ioncupric 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 – SO 4 2- sulfateSO 3 2- sulfite – NO 3 - nitrateNO 2 -nitrite

Common Anions

Chloroxyanions Polyatomic ions containing oxygen and chlorine FormulaName ClO - hypochlorite ClO 2 - chlorite ClO 3 - chlorate ClO 4 - perchlorate

Polyatomic Ions Some begin with hydrogen H + + CO 3 2- → HCO 3 - hydrogen carbonate H + + PO 4 3- → HPO 4 2- hydrogen phosphate H + + HPO 4 2- → H 2 PO 4 - dihydrogen phosphate

Polyatomic Cations Only 2 Ammonium Ion NH 4 + H + + :NH 3 → NH 4 + Hydronium Ion H 3 O + H + + H 2 O: → H 3 O +

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: SF 6 sulfur hexafluoride Example N 2 O 4 dinitrogen tetroxide

9.4 Formulas and Names of Acids & Bases Acids are compounds that have one or more ionizable hydrogens General formula H n X HCl (g) + H 2 O → H 3 O + + 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) NH 3 (g) + H 2 O → NH 4 + (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 H2O2H2O2 H2OH2O Mass O32 g16 g Mass H2 g Ratio O:H16:18:1 Ratio O:O16:8 = 2:1

Flow Chart to Name Chemical Compounds