Question

3. Write short answers.
a) What is meant by variable valency? Give two examples of elements which have variable valency.​

Answer 1

Answer:

Certain elements combine with other atoms, donating, accepting or sharing electrons in different proportions depending on the nature of the reaction. For example, iron combines with oxygen to form ferrous oxide as well as ferric oxide. 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.

2 examples are- Iron and Copper

Answer 2

certain elements combined with other atoms in the basis of their nature but in different proportion..

example : two atoms of hydrogen combined with one atom of oxygen to form water H2O so the valency of oxygen is 2.

it may be defined as a number of electrons that an atom denotes or accept to form the duplex state or octet state.