<span>Ca^(2+). Calcium is an alkaline earth metal with an atomic number of 20. Its electronic configuration is (2, 8, 8, 2). From the electronic configuration it would be observed that calcium has two valence electrons. Calcium shares these two electrons with non metals like sulphur in an ionic bond to obtain an outer shell which is full octet. Let me use Sulphur. When calcium gives out its two valence electrons its electronic configuration becomes (2, 8, 8) thereby obtaining a stable out shell and the calcium ion becomes Ca^(2+). The sulphur also obtains a stable octet because it has 6 valence electron initially.</span>
Atomic number shows the number of protons in an atom's nucleus. If the atomic number is 30, then it has 30 protons. The question says it is neutral, so it must have the same amount of protons and electrons.
