Question

Which of the following are true for an element?

(i) Atomic number= number of protons + number of electrons

(ii) Mass number= number of protons + number of neutrons

(iii) Atomic number= number of protons = number of neutrons

(iv) Atomic number= number of protons = number of electrons

• A. (i) and (ii)
• B. (i) and (iii)
• C. (ii) and (iii)
• D. (ii) and (iv)

Answer 1

The correct option is D

(ii) and (iv)

The correct option is (D).

Explanation of the correct option:

1. Atomic Number: is the number of protons present in the nucleus of an atom.

(i) Since an atom is electrically neutral the number of electrons is always equal to the number of protons

(ii) Thus Atomic Number= Number of protons= number of electrons.

2. Mass Number: is the sum of a number of neutrons and protons present in the nucleus of an atom.

Mass Number = Number of protons + Number of neutrons

Hence (i) Mass Number = Number of protons + Number of neutrons and (iv) Atomic Number= Number of protons= number of electrons are true statements.