How many electrons does the Mg+2 ion have?

10 electrons

Explanation:

The easiest way to do this is to simply look at the periodic table, find the atomic number of magnesium, and subtract 2 from it. The reason this works is that the atomic number tells you how many protons an element has. If we want the element to be neutral, then by definition it will have the same number of electrons.

10 Valence Electrons

Explanation:

Easiest thing to do is to look at your periodic table :)

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.