Question

What is the difference in number of neutrons in Protium and Deuterium?

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

The correct option is A 1

Isotopes of an element differ in the number of neutrons in their nuclei.
They have the same number of protons and electrons. Hence the same atomic number but a different mass number.

Protium and Deuterium,${}_1^{1}H$ and ${}_1^{2}H$, have the same atomic number and different mass number. They have 1 proton and 1 electron each. But they have 0 and 1 neutrons respectively.

So, the difference in the number of neutrons $=1$.