How many total orbitals are present in the $4f$ subshell?

In any atom,which sub-shell will have the highest energy among the following?

The five valence electrons of $_{15}P$ are represented as shown in the figure. If the spin quantum number of $B$ and $Z$ is $+1/2$,which of the following groups has three identical quantum numbers?

The order of filling of electrons in the orbitals of an atom will be

Nickel atom can lose two electrons to form $Ni^{2+}$ ion. The atomic number of nickel is $28$. From which orbital will nickel lose two electrons?

$A$: The energy of an electron can be determined by the principal quantum number.
$R$: The principal quantum number $(n)$ determines the possible distance of the electron from the nucleus.