Question

First and second ionisation enthalpies (in kj/mol) of few elements are given below :

Element	$IE_1$	$IE_2$
(i)	520	7300
(ii)	900	1760
(iii)	1680	3380
(iv)	2080	3963

Which of the above elements will form halides with formula $MX_2$ ?

• A. (i) and (ii)
• B. (i) and (iii)
• C. (ii) and (iii)
• D. (i) and (iv)

Answer 1

Answer: (C)

(ii) is a reactive metal from second group, and (iii) is a reactive non-metal from $17^{th}$ group.
For second group elements, the difference in successive $IE$ is less. The compound formed will be $MX_2$.