Explanation:
The atomic number of element (M) is 26 . According to Aufbau principle, the electronic configuration of ${ }_{26} \mathrm{M}$ will be $1 \mathrm{~s}^2, 2 \mathrm{~s}^2, 2 \mathrm{p}^6, 3 \mathrm{~s}^2, 3 \mathrm{p}^6, 3 \mathrm{~d}^6$, $4 \mathrm{~s}^2$
{lc}
|For | ${ }_{26} ^{3+}=1 ^2, 2 ^2, 2 ^6, 3 ^2, 3 ^6, 3 ^5$ |
|---|---|
|or | ${ }_{26} ^{3+}=2,8,13$ |
| K L M
Hence, the electrons are present in M shell is 13.