How many pairs are

CHEMISTRY · Subjective · A Level · Chemistry · Periodicity and periodic trends · Periodicity and periodic trends

Problem

How many pairs are, in which first species has lower ionisation energy than second species:


(i) N and O	(ii) Br and K	(iii) Be and B	(iv) I and $\text{I}^-$
(v) $\text{Li}$ and $\text{Li}^+$	(vi) O and S	(vii) Ba and Sr