Which of the following best explains why calcium forms Ca2+ ions rather than Ca+ ions in ionic compounds?
a) The second ionization energy of calcium is lower than the first, so removing two electrons is energetically favorable.
b) Calcium forms a +2 ion so that it can pair with two Cl− ions and make neutral CaCl2.
c) Removing two electrons gives calcium the noble-gas electron configuration of argon, which is highly stable.
d) Calcium’s 20 protons create such a strong positive nucleus that the atom must carry a +2 charge to remain balanced.