Which of the following are degenerate orbitals?
$3d_{xy}, 4d_{xy}, 3d_{z^2}, 3d_{xz}, 4d_{yz}, 4d_{z^2}$

Total number of ions from the following with noble gas configuration is . . . . . . .
$Sr^{2+} (Z=38), Cs^{+} (Z=55), La^{2+} (Z=57), Pb^{2+} (Z=82), Yb^{2+} (Z=70) \text{ and } Fe^{2+} (Z=26)$

Statement $1$: The energy of an electron is determined by the principal quantum number.
Statement $2$: The principal quantum number $(n)$ indicates the distance of the electron from the nucleus.

Electronic configuration of $C$ is

$d_{z^2}$ orbital has :

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