Q. The alpha-particle carries two positive charges. Its mass is very nearly equal to that of? Answer:
an atom of helium
Notes: Each alpha particle contains two protons and two neutrons. Total number of nucleons = Number of protons + Number of neutrons = 2 + 2 = 4 Total number of nucleons = Mass number of an element Thus mass number of alpha particle is 4 which is equal to molecular weight of helium atom.