Assertion (A): The valency of an element is its combining capacity with an atom of another element.

Reason (R): Elements take part in chemical combination to acquire the electronic configuration of the nearest noble gas.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Both A and R are true but R is not the correct explanation of A.

Explanation — Valency of an element is the combining capacity of that element with other elements and is equal to the number of electrons that take part in a chemical reaction. Hence the assertion (A) is true. The atoms of all elements, other than the inert gases, combine to attain a stable configuration of nearest noble gas. Hence the reason (R) is true.
However, reason (R) is not the correct explanation of assertion (A), because valency is defined by how many electrons are involved in bonding, not by why the atom bonds (which R explains). Hence, while both statements are correct individually, reason (R) doesn’t directly explain assertion (A).