Question

Which of the following is a constituent particle of an atom?
(a) electron
(b) proton
(c) neutron
(d) all of the above

Answer 1

Hint: An atom is the smallest unit of ordinary matter that forms a chemical element. Every solid, liquid, gas and plasma are composed of neutral or ionized atoms. After that J.J Thomson discovered electrons are divisible into subatomic particles. Atom is composed of these subatomic particles.

Complete step by step answer:
- All matter is made up of atoms. It was believed that atoms are indivisible and are fundamental units of matter. The word atom is derived from the Greek word Atomos, which means indivisible.
- But, J.J Thomson experiments with cathode ray tubes showed that all atoms contain charged subatomic particles. Thomson proposed the plum pudding model of the atom, which had negatively charged electrons embedded within a positively charged soup.
Atoms are made up of: protons, neutrons and electrons.
- Let’s think of protons and neutrons together forming as sun or nucleus, at the center of the system. The electrons orbit this nucleus, like planets. If atoms are impossibly small, these subatomic particles are even more so.
So, the constituent particles of an atom are electron, proton and neutron.
The correct answer is option “D” .

Note: Many other basic atomic particles are also emitted through radioactive decay like alpha particles, beta particles. Also, many forms of radioactive decay emit gamma rays, which are not particles.