Single Choice

If Hund's rule is not followed, magnetic moment if Fe$$^{2+}$$, Mn$$^\oplus$$ and Cr all having 24 electrons will be in order :

AFe$$^{2+}$$< Mn$$^\oplus$$ < Cr
BFe$$^{2+}$$ = Cr < Mn$$^\oplus$$
Correct Answer
CFe$$^{2+}$$ = Mn$$^\oplus$$ < Cr
DMn$$^{2\oplus}$$ = Cr < Fe$$^{2+}$$

Solution

According to Hund's rule, electrons are distributed among the orbitals of subshell in such a way as to give maximum number of unpaired electron with parallel spin. i.e. in a subshell pairing of electron will not start until and unless all the orbitals of that subshell will get one electron each with same spin. So, $$Mn^+$$ have 2 unpaired electron, Cr have zero unpaired electron and $$Fe^{+2}$$ have zero unpaired electron and order is $$Fe^{2+} = Cr < Mn^\oplus$$.

SIMILAR QUESTIONS

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