The loss or gain of a neutron in the nucleus results in the formation of what?

transmutation

Explanation:

Transmutation is the transformation of one element into another by one or a series of nuclear decays or reactions.

Alpha decay occurs when an unstable nucleus emits an alpha particle, which is identical to a helium-4 nucleus (42He), which contains two neutrons and two protons. This decreases the mass number by four and the atomic number by two. So, since the atomic number decreases, the parent isotope is transmutated to a different isotope (daughter isotope). For example, seaborgium-263 (263106Sg) undergoes alpha decay to form rutherfordium-259, (259104Rf).