JEE Main · 2021 · 31 Aug 2021 · Shift 1 · Atomic Structure

Germanium in its ground state is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^2$. An orbital with $m_l=0$ is each $s$ orbital together with the single $m_l=0$ orbital inside every $p$ and $d$ subshell. The filled $1s,2s,3s,4s$ give four such orbitals, the filled $2p$ and $3p$ sets each contribute their one $m_l=0$ orbital, and the filled $3d$ set contributes its $m_l=0$ orbital; the half-filled $4p^2$ contributes none, since its two electrons occupy separate $p$ orbitals. Seven completely filled orbitals have $m_l=0$.