Nucleon is a common name for:
A. Proton and electron.
B. Electron and neutron.
C. Neutron only.
D. Neutron and proton.

Hint: Subatomic particles found in the nucleus of an atom are referred to as nucleons. The nucleus is formed by protons and neutrons.

Complete step by step answer:
An atom consists of protons, electrons and neutrons. These are also termed as subatomic particles. The electrons revolve around the nucleus in orbits. Protons and neutrons make up the nucleus. Hence, these particles are also called nucleons. Electrons do not form the nucleus of an atom. They revolve in orbits outside the nucleus. Hence, they cannot be referred to as nucleons. Also, neutrons alone cannot be termed as nucleons as both protons and neutrons are found in the nucleus of an atom. Although, a hydrogen atom has only a single proton in its nucleus and that can be referred to as a nucleon. The protons and neutrons are held together inside the nucleus by the nuclear force.

So, the correct answer is “Option D”.

Additional Information:
The total number of nucleons is denoted by the mass number of an atom. Mass number is calculated by adding the number of protons and the number of neutrons in the nucleus of an atom.

Note:
We should not get confused between nucleons and neutrons. Although they sound very similar, they are different. Nucleons cannot be termed as elementary particles as they are made up of smaller particles called ‘quarks’.