Quick question: ionization question?

I have a quick chemistry question about the concept of highest first ionization energy.

The question reads, which of the following species will have the highest ionization energy. Cl-, Ar, K+, S2-

Just to verify, wouldn’t the answer be K+?

1 Answer

  • The ionization energy is the energy required to remove an electron. Removing an an electron from Cl- or S^2- would require less energy than needed for the respective neutral atom due to the repulsion between the existing electrons and the “extra” electrons.

    Removing an electron from K+ requires removing it from an “inner” energy sublevel which is closer to the nucleus and would require a great deal of energy. The ionization energy for K+ is actually the second ionization energy of K, and is quite high.

    Electron configuration of K

    1s2, 2s2 2p6, 3s2 3p6, 4s1

    The first ionization energy is the energy needed to remove the 4s electron. The second ionization energy is the energy required to remove a 3p electron, which is considerably more energy.

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