The maximum number of unpaired electrons that can be present in $d$-orbitals is

In an atom,if the $K$-shell has $2$ electrons,the $L$-shell has $8$ electrons,and the $M$-shell has $6$ electrons,what is the total number of electrons in the atom?

An element has the electronic configuration $1s^2, 2s^2 2p^6, 3s^2 3p^2$. Its valence electrons are

When the $4d$ orbital is complete,the newly entering electron goes into which orbital?

For a magnetic quantum number $m = 0, \pm 1$,the value of the principal orbital (azimuthal quantum number $l$) corresponds to which subshell,and what is the minimum principal quantum number $n$ required for this set?

Which of the following sets of quantum numbers is not allowed?