(i) Write the electronic configurations of the following ions: (a) $H^{-}\left(b\right){Na}^{+}\left(c\right)O^{2-}\left(d\right)F^{-}$.
(ii) What are the atomic numbers of elements whose outermost electrons are represented by $\left(a\right){3s}^1\left(b\right){2p}^3$ and $\left(c\right){3d}^1$ ?
(iii) Which atoms are indicated by the following configurations ?
(a) $\left[He\right]2s^1$ (b) $\left[Ne\right]{3s}^2{3p}^3$ (c) $\left[Ar\right]{4s}^2{3d}^1$

(i) (a) The electronic configuration of $H^{-}$ is $1s^2$
(b)The electronic configuration of ${Na}^{+}$ is $1s^2{2s}^2{2p}^6$
(c)The electronic configuration of $O^{2-}$ is $1s^2{2s}^2{2p}^6$
(d) The electronic configurations of $F^{-}$ is $1s^2{2s}^2{2p}^6$
(ii) The atomic numbers of elements whose outermost electrons are represented by $\left(a\right){3s}^1\left(b\right){2p}^{3}and\left(c\right){3d}^1$ are 11 (Na), 7 (N) and 21 (Sc) respectively.
(iii) The following configurations indicates
(a) $\left[He\right]2s^1$ (b) $\left[Ne\right]{3s}^2{3p}^3$ (c) $\left[Ar\right]{4s}^2{3d}^1$
(a) Li $(Z=3)$, (b) P$(Z=15)$ and (c) Sc $Z=21)$ respectively.