Unit 5 - Writing formulas of Ionic Compounds

Write the formula for Aluminum Arsenide.

Cation formula: Al (+3 charge) (Aluminum) Anion formula: As (-3 charge) (Arsenic) Add them together & "criss-cross" charges: Al3As3 Simplify: AlAs3

Write the chemical formula for Barium Nitride.

Cation formula: Ba (+2 charge) (Barium) Anion formula: N (-3 charge) (Nitrogen) Add them together & "criss-cross" charges: Ba3N2 (need 3 Bariums to equal the charge of 2 Nitrogens) Simplify: Ba3N2 (no simplification needed)

Write the chemical formula for Calcium Sulfide.

Cation formula: Ca (+2 charge) (Calcium) Anion formula: S (-2 charge) (Sulfur) Add them together & "criss-cross" charges: Ca2S2 Simplify: CaS

Write the formula for Potassium Selenide.

Cation formula: K (+1 charge) (Potassium) Anion formula: Se (-2 charge) (Selenium) Add them together & "criss-cross" charges: K2Se (need 2 Potassiums to equal the charge of 1 Selenium) Simplify: K2Se (no simplification needed)

Write the formula for Magnesium Fluoride.

Cation formula: Mg (+2 charge) (Magnesium) Anion formula: F (-1 charge) (Fluorine) Add them together & "criss-cross" charges: MgF2 (need 2 Fluorines to equal the charge of 1 Magnesium) Simplify: MgF2 (no simplification needed)