Which ion was formed by providing the second ionization energy to remove an electron?

The second ionization energy removes an electron from an atom that has already lost one electron, forming a 2+ ion. Calcium loses two electrons to form Ca²⁺, so this is the ion associated with the second ionization. N³⁻ and S²⁻ are negative ions formed by gaining electrons, while Fe³⁺ requires removing three electrons.

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