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Q.
Which of the following is most stable among $ C{{u}^{+}},\,F{{e}^{+}},F{{e}^{2+}} $ and $ F{{e}^{3+}} $ ?
BVP MedicalBVP Medical 2001
Solution:
$ F{{e}^{3+}} $ electronic configuration $ 3{{s}^{2}}3{{p}^{6}}3{{d}^{5}}, $ has half-filled d-orbital is more stable than $ C{{u}^{+}},F{{e}^{+}} $ arid q $ F{{e}^{2+}} $ . $ C{{u}^{+}} $ electronic configuration $ 3{{s}^{2}}3{{p}^{6}}3{{d}^{10}} $ although having fully-filled 3rd shell is less stable because nuclear charge (29 protons) on $ Cu $ is not sufficient enough to hold 28 electrons.