Write down the formulae of (i) Sodium Oxide (ii) Aluminium Chloride (iii) Sodium Sulphide (iv) Magnesium Hydroxide

 

Answer

(i) Sodium Oxide

It contains 2 elements Sodium(Na) and Oxygen(O)

  • Valency of Sodium (Na) is 1
  • Valency of Oxygen (O) is 2

 

These valencies interchange while writing formula as shown below

 

(ii) Aluminium Chloride 

It contains 2 elements Aluminium(Al) and Chlorine(Cl)

  • Valency of Aluminum (Al) is 3
  • Valency of Chlorine (Cl) is 1

 

These valencies interchange while writing formula as shown below

Hence, the formula becomes AlCl 3

 

(iii) Sodium Sulphide

It contains 2 elements Sodium(Na) and Sulphur(S) 

Valency of Sodium (Na) is 1

Valency of Sulphur (S) is 2

 

These valencies interchange while writing formula as shown below

Hence, the formula becomes Na 2 S

 

(iv) Magnesium Hydroxide

It contains 2 elements Magnesium(Mg) and Hydroxide(OH)

Valency of Magnesium (Mg) is 2

Valency of Hydroxide (OH) is 1

 

These valencies interchange while writing formula as shown below

Hence, the formula becomes Mg(OH) 2

 

  1. Class 9
  2. Chapter 3 Class 9 - Atoms And Molecules (Term 2)

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CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo