Rules For Writing Chemical Formulas and Naming CompoundsIPC 2007

Binary Ionic Compounds

• Binary compound - made of two elements

• Oxidation number – tells you how many electrons an atom loses or gains to form an ionic compound; positive or negative; (become stable)

• Some metals can have more than one oxidation number

Compounds are neutralFor every positive, there must be a negative

• Group 1 is + 1

• Group 2 is +2

• Group 13 is +3

• Group 14 is +4

• Group 15 is -3

• Group 16 is -2

• Group 17 is -1

• Group 18 is 0

Writing Formulas

• 1.Write the symbol of the element or polyatomic ion (ions containing more than one atom) that has the positive oxidation number. Hydrogen and ammonium (NH4) and all metals are positive.

Writing Formulas

• 2. Write the symbol of the element or polyatomic ion with the negative oxidation number. Nonmetals other than hydrogen and polyatomic ions other than NH4 are positive.

• 3. Use subscripts next to each ion so that the total charge of all ions is zero.

Practice

• Calcium and Chlorine

• Potassium and Sulfur

• Hydrogen and Oxygen

• Magnesium and Oxygen

• Lithium and Nitrogen

• Sodium and Chlorine

• Calcium and Chlorine