Question

An element x shows a variable valency 3 & 5. What are the formulas of the oxide formed by it.​

Answer 1

Explanation:

Let the element be "X"

Case-1. Valency of X = +3

Valenvy of Oxide "O" =-2

Therefore, the formula for the oxides of the Element

X = X2O3

Case-2. valency of X = +5

valency of O = -2

Therefore, the formula for the oxides of the element X = X2O5

Answer 2

The formulas of the oxide formed by the element 'X' which shows variable valencies 3 and 5 are X₂O₃ and X₂O₅.

• The valency of oxide is -2.
• oxygen has gained 2 electrons to complete its octet.
• The valency of the element 'X' is 3 and 5.
• By the criss-cross method, we get

      ⇒   X   O        

       ⇒  +3    -2

        ⇒ X₂O₃

•        X  O

         ⇒ 5    -2

         ⇒   X₂O₅

Hence, the formulas of the oxide formed by the element 'X' which shows variable valencies 3 and 5 are X₂O₃ and X₂O₅.