Which equation below represents the second ionization energy of nickel?

• A. Ni^+(g) → Ni^{2+}(g) + e^-
• B. Ni^{2+}(g) → Ni^{3+}(g) + e^-
• C. Ni(g) → Ni^+(g) + e^-
• D. Ni(s) → Ni^+(g) + e^-

Answer: (A)

Verified step by step guidance

1. Understand that ionization energy refers to the energy required to remove an electron from an atom or ion in the gas phase.
2. Recall that the first ionization energy corresponds to removing one electron from a neutral atom, forming a +1 ion: \(\mathrm{Ni(g) \rightarrow Ni^{+}(g) + e^{-}}\).
3. The second ionization energy involves removing a second electron, but this time from the already formed +1 ion, resulting in a +2 ion: \(\mathrm{Ni^{+}(g) \rightarrow Ni^{2+}(g) + e^{-}}\).
4. Identify that the other options either represent the first ionization energy, the third ionization energy, or involve the solid state, which is not relevant for ionization energy calculations that always consider gaseous species.
5. Conclude that the correct equation for the second ionization energy of nickel is the one showing the removal of an electron from \(\mathrm{Ni^{+}(g)}\) to form \(\mathrm{Ni^{2+}(g)}\).