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Q.
The atomic number of an element $M$ is $26$. How many electrons are present in the $M$-shell of the element in its state
UP CPMTUP CPMT 2008
Solution:
It is an example of Fe atom
$Fe \to K \to 1 s^{2}$
$L \to 2s^{2}\,2p^{6}$
$M \to 3s^{2}\,3p^{6}\,3d^{6}$
$N \to 4s^{2}$
$Fe^{3+} \to K \to 1s^{2}$
$L \to 2s^{2}\,2p^{6}$
$M \to 3s^{2}\,3p^{6}\,3d^{5}$
Total number of electrons in M shell is $13$