KVPY 2019 SA Exam Previous Papers

(i) E = $-13.6\times \frac{{\mathit{z}}^2}{{\mathit{n}}^2}$ Application only for single electron species.
For 2S ⇒ n=2
Order of energy ${\mathit{E}}_{\mathrm{2}\mathit{s}}\left(\mathit{H}\right)>{\mathit{E}}_{2\mathit{s}}\left(\mathit{L}\mathit{i}\right)>{\mathit{E}}_{2\mathit{s}}\left(\mathit{N}\mathit{a}\right)>{\mathit{E}}_{2\mathit{s}}\left(\mathit{K}\right)$
(ii) Maximum number of electron which can accommodate in a principal energy shell is equal to 2n${}^2$.
(iii) Extra stability of half -field subshell is due to to higher exchange energy.
(iv) Only two electron with opposite spin can exists in same orbital.
So correct statement – (i), (ii).