Provide the four quantum numbers for the two outermost electrons of $Ca$ $(Z = 20)$.

The orbital with maximum energy is

Consider the following pairs of electrons:
$(A)$ $(a)$ $n=3, l=1, m_{l}=1, m_{s}=+\frac{1}{2}$
$(b)$ $n=3, l=2, m_{l}=1, m_{s}=+\frac{1}{2}$
$(B)$ $(a)$ $n=3, l=2, m_{l}=-2, m_{s}=-\frac{1}{2}$
$(b)$ $n=3, l=2, m_{l}=-1, m_{s}=-\frac{1}{2}$
$(C)$ $(a)$ $n=4, l=2, m_{l}=2, m_{s}=+\frac{1}{2}$
$(b)$ $n=3, l=2, m_{l}=2, m_{s}=+\frac{1}{2}$
The pair$(s)$ of electrons present in degenerate orbitals is/are...... .

Which electronic configuration for oxygen is correct according to Hund's rule of maximum multiplicity?

Which of the following does not have valence electrons in the $3d-$subshell?

The energy of a $2p$ orbital in a multi-electron atom is