Write the electronic configuration of the following ions:
$(a) H^-$
$(b) Na^+$
$(c) O^{2-}$
$(d) F^-$

In the ground state of atomic $Fe \,(Z = 26)$,the spin-only magnetic moment is ...... $\times 10^{-1} \,BM$. (Round off to the nearest integer).
$[$Given $: \sqrt{3} = 1.73, \sqrt{2} = 1.41]$

What are the electronic configurations of elements with atomic numbers $Z = 117$ and $Z = 120$?

Statement $A$: An orbital can accommodate a maximum of two electrons.
Reason $R$: Two electrons in an orbital produce opposite magnetic fields.

The hydrogen-like species $Li^{2+}$ is in a spherically symmetric state $S_1$ with one radial node. Upon absorbing light,the ion undergoes transition to a state $S_2$. The state $S_2$ has one radial node and its energy is equal to the ground state energy of the hydrogen atom.
$1.$ The state $S_1$ is
$(A)$ $1s$ $(B)$ $2s$ $(C)$ $2p$ $(D)$ $3s$
$2.$ Energy of the state $S_1$ in units of the hydrogen atom ground state energy is
$(A)$ $0.75$ $(B)$ $1.50$ $(C)$ $2.25$ $(D)$ $4.50$
$3.$ The orbital angular momentum quantum number of the state $S_2$ is
$(A)$ $0$ $(B)$ $1$ $(C)$ $2$ $(D)$ $3$
Give the answer for questions $1, 2$ and $3.$

How many electrons can be accommodated in a sub-shell for which $n = 3, l = 1$?