The alpha particle carries two positive charges. Its mass is very nearly equal to that of:

1. Two protons
2. An atom of helium
3. Sum of masses of two positrons and two neutrons
4. Two positrons as each positron carries a single positive charge

Explanation

Option (b) is correct

• An alpha particle is the nucleus of a helium atom. It contains 2 protons and 2 neutrons, giving it a +2 charge. Since it lacks electrons, its mass is almost equal to a helium atom (electron mass is negligible).

Answer: (b) An atom of helium