Question

Isotopes of an element have different number of neutrons.

• A. neutrons
• B. protons

Answer 1

The correct option is A

neutrons

$\bullet$ Isotopes of an element have the same atomic number but different mass number.

$\bullet$ Mass number = number of neutrons + number of protons

$\bullet$ Atomic number = number of protons

$\bullet$ Isotopes have different number of neutrons and hence, have different mass number.

$\bullet$ For example, hydrogen has three isotopes, i.e., protium, deuterium and tritium (${}_1^{1}H$, ${}_1^{2}H$, ${}_1^{3}H$).

All of these have same atomic number, but different mass number, hence, different number of neutrons.