Identify the elements X and Y using the ionisation energy values given below :

	Ionization energy (kJ/mol)
	1$${st}$$	2$${nd}$$
X	495	4563
Y	731	1450

Which pair of oxides is acidic in nature?

The correct order of electron gain enthalpy is :

Match List - I with List - II.

	List I Electronic configuration		List II $${\Delta _i}H$$ in kJ $$mo{l^{ - 1}}$$
(a)	$$1{s^2}2{s^2}$$	(i)	801
(b)	$$1{s^2}2{s^2}2{p^4}$$	(ii)	899
(c)	$$1{s^2}2{s^2}2{p^3}$$	(iii)	1314
(d)	$$1{s^2}2{s^2}2{p^1}$$	(iv)	1402

Choose the most appropriate answer from the options given below :