Which of the following elements has a half-filled valence shell?

The number of unpaired electrons in the excited state of carbon is equal to the number of unpaired electrons in which of the following?

Consider the following statements:
$(A)$ The principal quantum number $'n'$ is a positive integer with values of $'n'=1, 2, 3, \dots$.
$(B)$ The azimuthal quantum number $'l'$ for a given $'n'$ (principal quantum number) can have values as $'l'=0, 1, 2, \dots, (n-1)$.
$(C)$ Magnetic orbital quantum number $'m_l'$ for a particular $'l'$ (azimuthal quantum number) has $(2l+1)$ values.
$(D)$ $\pm 1/2$ are the two possible orientations of electron spin.
$(E)$ For $l=5$,there will be a total of $11$ orbitals.
Which of the above statements are correct?

The correct set of four quantum numbers for the valence electron of rubidium atom $(Z=37)$ is:

Which of the following ions does not have the same electronic configuration as $Ne$?

Beryllium's fourth electron will have the four quantum numbers :