An alpha particle is composed of

A. nothing

B. two protons and two neutrons

C. one proton and no neutrons

D. one neutron no protons

Answer: B. two protons and two neutrons

Explanation: Alpha rays are fast moving streams of positively charged particles which are shown to be helium nuclei represented by 4He2, having a mass number of 4, i. e., having 2 protons and 2 neutrons. Mass number of an element is the sum of the number of protons and neutrons in the nucleus of an atom. A helium atom has 2 protons and 2 neutrons in its atom.

B. Two protons and two neutrons