9.1 Naming Ions

• When the metals in Groups 1A, 2A, and 3A lose electrons, they form cations with positive charges equal to their group number.
• The charge of any ion of a Group A nonmetal is determined by subtracting 8 from the group number.
• The charges of cations of many transition metal ions must be determined from the number of electrons lost. When a cation can have more than one ionic charge, a Roman numeral is used in the name to indicate the charge.
• The names of most polyatomic anions end in -ite or -ate.

9.2 Naming and Writing Formulas for Ionic Compounds

• The name of a binary ionic compound is the cation name followed by the anion name.
• To write the formula for a binary ionic compound, write the symbol for the cation and then the anion. Then balance the charges.
• To write formulas for compounds containing polyatomic ions, write the symbol for the metal ion followed by the formula for the polyatomic ion and balance the charges.
• To name a compound containing a polyatomic ion, state the cation first and then the anion.

9.3 Naming and Writing Formulas for Molecular Compounds

• Prefixes show how many atoms of each element are present in a molecule of a binary compound.
• To write the formula for a binary molecular compound, write the symbols for the elements and use the prefixes to determine the subscripts. Omit mono-for a single atom.

9.4 Naming and Writing Formulas for Acids and Bases

• An acid is a combination of a monatomic or polyatomic anion with sufficient hydrogen atoms to make the compound electrically neutral.
• A base is a combination of a cation with as many hydroxide ions as are needed to make the compound electrically neutral. Bases are named in the same way as other ionic compounds.

9.5 The Laws Governing Formulas and Names

• The ways that compounds form are summed up in two laws: the law of definite proportions and the law of multiple proportions.