Which one of the following could form an atom by the addition of electrons only?

Question

Which one of the following could form an atom by the addition of electrons only?
• an alpha particle
• a beta particle
• a negative ion
• a neutron
• a photon

Answer 1

The answer is an alpha particle.  Alpha particles are helium nuclei  (He²⁺⁾.  Adding two electrons to each particle yields helium atoms.