Everything Science Grade 11

CHAPTER 1. ATOMICCOMBINATIONS 1.9

Name of compound ion formula

Carbonate CO^23 −

Sulfate SO^24 −

Hydroxide OH−

Ammonium NH+ 4

Nitrate NO− 3

Hydrogen carbonate HCO− 3

Phosphate PO^34 −

Chlorate ClO− 3

Cyanide CN−

Chromate CrO^24 −

Permanganate MnO− 4

Table 1.2: Table showing common compound ions and their formulae

Example 10: Formulae of ionic compounds

QUESTION

Write the chemical formula for potassium iodide.

SOLUTION

Step 1 : Write down the ions that make up the compound.

Potassium iodide contains potassium and iodideions.

Step 2 : Determine the valencyand charge of each ion.

Potassium iodide contains the ions K+(valency = 1; charge =+1) and I−

(valency = 1; charge =-1). In order to balancethe charge in a single molecule,

one atom of potassium will be needed for every one atom of iodine.

Step 3 : Write the chemical formula

The chemical formula for potassium iodide is therefore:

KI

Example 11: Formulae of ionic compounds