Question

An isotope of helium is represented by the symbol ${}_2^{3}He$ How many protons, neutrons and electrons are there in an atom of the isotope?

• A. Proton:- 1 Neutron:- 2 Electron:- 1
• B. Proton:- 1 Neutron:- 3 Electron:- 2
• C. Proton:- 2 Neutron:- 1 Electron:- 2
• D. Proton:- 2 Neutron:- 3 Electron:- 2

Answer 1

The correct option is C

Proton:- 2

Neutron:- 1

Electron:- 2

Isotopes are atoms of the same element having the same atomic number (number of protons) but different mass number (number of protons + number of neutrons).

Atomic number (number of proton) = 2 and number of electron = number of proton = 2

Mass number = Number of proton + Number of neutron

Let 'x' be number of neutron

3 = 2 + x

x = 1

Number of proton, neutron, and electron in ${}_2^{3}He$ is 2, 1 and 2.