What is the mass number of an element, the atom of which contains two protons, two neutrons and two electrons?

Correct answer: (b) 4

Explanation

Mass number (A) = protons + neutrons; electrons do not count as they have negligible mass.

With 2 protons and 2 neutrons, A = 2 + 2 = 4, identifying the atom as Helium (He).

Helium has atomic number 2 and mass number 4, so the count of electrons is irrelevant to A.