Question

Which one of the following option is incorrect?

(a) Elements are defined by the number of protons they possess.

(b) Isobars are atoms having the same atomic number but different mass number.

(c) The mass number of an atom is equal to the number of nucleons in its nucleus.

(d) Valency is the combining capacity of an atom.

Answer 1

(d) Valency is the combining capacity of an atom.

Atoms of different elements with different atomic number but same mass number are known as isobars.