Question

How many unpaired electrons are there in a strong field iron(II) octahedral complex

Answer 1

There are zero unpaired electrons in strong field Fe(II) octahedral complex.

Electronic configuration of $Fe$ is $\space3d^6\space4s^2$

Electronic configuration of $Fe(\Iota\Iota)$ is $3d^6\space 4s^0$

Because, 2 electrons are removed from $4s$ orbital of the $Fe(\Iota\Iota)$.

In a strong field, $d^6$ electrons are split into $t_{2g}^6$ and $e_g^0$ . These 6 electrons in $t_{2g}$ are paired. So there is no unpaired electron in the octahedral complex.