Chapter 2 Atoms, Molecules, and Ions 1

Molecules and Molecular Compounds A diatomic molecule is a molecule that is made up of two atoms A molecular formula indicates the actual numbers and types of atoms in a molecule. An empirical formula is the lowest whole-number ratio of atoms in a molecule. 2

Molecules and Molecular Compounds A structural formula of a substance shows which atoms are attached to which within the molecule. 3

Ions and Ionic Compounds An ion with a positive charge is a cation. An ion with a negative charge is an anion. A polyatomic ion is a group of atoms joined as a molecule with an overall net charge. 4

Ions and Ionic Compounds An ionic compound is a compound that contains both positively and negatively charged ions. 5

Naming Inorganic Compounds Positive Ions (Cations) a) Cations have the same name as their metal b) If a metal can form different cations, the positive charge is indicated by a Roman numeral in parentheses following the name of the metal Na + sodium ion Zn 2+ zinc ion Al 3+ aluminum ion Fe 3+ iron(III) ion Fe 2+ iron(II) ion Cu + copper(I) ion Cu 2+ copper(II) ion 6

Names and Formulas of Acids Acids of monatomic anions are called binary acids. Acids of oxyanions are called oxyacids. Binary Acids Oxyacids HF hydrofluoric acid HNO 3 nitric acid HCl hydrochloric acid H 2 SO 4 sulfuric acid HBr hydrobromic acid HClO 4 perchloric acid H 2 S hydrosulfuric H 2 SO 3 sulfurous acid H 2 Se hydroselenic acid HClO 3 chloric acid 7

Names and Formulas of Acids To name binary acids replace the –ide ending with –ic acid and add the prefix hydro- To name oxyacids, replace the –ate ending of the oxyanion with –ic acid or the –ite ending with –ous acid ____ide become hydro____ic acid Bromide, Br -, becomes hydrobromic acid, HBr ____ate becomes ____ic acid Nitrate, NO 3 -, becomes nitric acid, HNO 3 ____ite becomes ____ous acid Sulfite, SO 3 2-, becomes sulfurous acid, H 2 SO 3 8

Names of Binary Molecular Compounds A binary molecular compound contains two nonmetals. The rules for naming binary molecular compounds are: 1. Name the first element. 2. Name the second element giving it an – ide ending. 3. Use prefixes to denote how many of each element are in the formula. 9

Names of Binary Molecular Compounds PrefixMeaning Mono-1 Di-2 Tri-3 Tetra-4 Penta-5 Hexa-6 Hepta-7 Octa-8 Nona-9 Deca-10 10