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Oct23-06, 06:43 PM
P: 12
Well, first of all, the first ionization enrgy of Ca is greater than that of K because Calcium's nucleus is more effective due to an increased effective nuclear charge. Next, the second ionization energy of Calcium is less than that of K because it is removing an electron from a more excited orbital than the orbital the second electron from K is being removed from. The second ionization energy of K is also about 6x greater than its first ionization energy because it is pulling an electron from a less excited orbital with less shielding and is closer to the nucleus, wheras the second electron being removed from calcium is from the same orbital as before.
I hope that I answered your question!