Question

Variable valency is a property of:
(A) Alkali metals
(B) Transition metals
(C) Alkaline earth metals
(D) Inert gases

Answer 1

Hint: We should know that certain elements combine with other atoms, donating, accepting, or sharing electrons in different proportions depending on the nature of the reaction. These are mainly d-block elements. Now try to answer this accordingly.

Complete step by step answer:

Let’s discuss the stepwise answer to this question -

Valency is defined as the combining capacity of an element. For example, the valency of Hydrogen is 1 as it has one electron in its outermost shell and requires one electron to become stable.

Some elements differ in their capacity to combine with other elements depending on the nature of the reaction; this property is called variable valency. For example, In the formation of ferrous oxide, iron exhibits a valency of +2, whereas, in ferric oxide, it has a valency of +3. This is termed variable valency.

In transition metals, (n−1) d and ns electrons have nearly the same energy level. Hence, most of these electrons take part in chemical bonding. Hence, transition metals show variable valency.

Therefore, we can conclude that the correct answer to this question is option B.

Note: We should also know that nonmetals such as nitrogen and oxygen also show variable valency. The products formed as a result of reaction with the different valency atoms differ in their properties.
For example, hydrogen shows a valency of +2 in hydrogen peroxide and a valency of +1 in case of water; hydrogen peroxide is strongly acidic in nature, whereas water is neutral.