What is the maximum number of electrons an M shell of the atom can accomodate?
The maximum number of electrons that can be accommodated in a shell is given by the formula 2n2, where n denotes the shell number. Thus, since for the K shell, n = 1, hence the maximum number of electrons that can be accommodated in the K shell is 2×(1)2=2
If, however, a given shell is the outermost shell, it cannot hold more than 8 electrons.
Similarly for M, the value of n = 3,
so no of electrons = 2×(3)2=18
Therefore, the M shell can hold a maximum of 18 electrons, but if it is the outermost shell, then it cannot hold more than 8 electrons.