What is the maximum number of electrons in the M-Shell ?

The maximum number of electrons that can be accommodated in a shell is determined by the formula 2n², where 'n' represents the principal quantum number or the shell number. The shells are designated alphabetically starting from the nucleus as K (n=1), L (n=2), M (n=3), and N (n=4). For the M-shell, the principal quantum number n is 3. Applying the formula, the maximum capacity is calculated as 2 × (3)² = 2 × 9 = 18 electrons. This capacity is distributed across three subshells: the 3s (2 electrons), 3p (6 electrons), and 3d (10 electrons) orbitals. While the octet rule states that the outermost shell of an atom cannot have more than 8 electrons during chemical stability, the total theoretical capacity of the third (M) shell remains 18.