01 Introduction to Chemistry
02 Matter and the Atomic Structure
03 The Mole Concept, Chemical Formula and Equation
04 The Periodic Table of Elements
05 Chemical Bond
06 Acids, Bases and Salts
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3.3.5 Formula of Ionic Compounds

Chemical Formlula of Ionic Compounds

2 Requirements to form the formula of an ionic compound

  1. Have at least 2 types of ions that contain opposite charge.
  2. The amount of positive charge/charges must be equal to the amount of negative charge/charges in the compound.

Example 1 – If the Charge of the Positive Ions = Charge of Negative Ions
Write the formula of each of the following compound

  1. Potassium bromide
  2. Sodium chloride

Answer:
a. Potassium bromide

b. Sodium chloride

Example 2 – If the Charge of the Positive Ions ≠ Charge of Negative Ions

Write the formula of each of the following compound
  1. Calcium iodide
  2. Sodium oxide

Answer:

a. Calcium iodide

b. Sodium oxide

Example 3 – If there is more than 1 element in the ion

Write the formula of each of the compound
  1. Ammonium sulphate
  2. Zinc nitrate

Answer:
a. Ammonium sulphate

b. Zinc nitrate

Example 4 – Formulae of Acid

Write the formula of the following acid
  1. Hydrochloric acid
  2. Sulphuric acid
  3. Nitric acid
  4. Ethanoic acid
  5. Phosphoric acid
  6. Carbonic acid

Answer:
a. Hydrochloric acid

b. Sulphuric acid

c. Nitric acid

d. Ethanoic acid

e. Phosphoric acid

f. Carbonic acid