Final answer:
A calcium ion would lose 2 electrons to form a stable Ca²⁺ ion, matching the electron configuration of the nearest noble gas, argon.
Step-by-step explanation:
The calcium ion would lose 2 electrons. When a neutral calcium atom, which has an atomic number of 20, meaning it has 20 protons and 20 electrons, forms an ion, it will lose electrons to achieve a noble gas electron configuration. Calcium is an alkaline earth metal (group 2 in the periodic table), and these metals typically lose two electrons to form a cation with a 2+ charge. This is because losing two electrons gives them the same number of electrons as the nearest noble gas, argon, in this case, resulting in a stable electron configuration. Thus, the correct answer for a calcium ion is that it would lose 2 electrons (C).