Question

Compound X is made of two elements . One element has the second highest ionisation energy value of first ionisation energy in it's group and the other element has the third highest value of first ionisation energy in it's group . Which compounds could be X
A) calcium chloride
B) magnesium bromide
C) potassium sulfide
Explain ?

Answer 1

Compound X = $\bold{\underline{Calcium \ Chloride}}$

Calcium comes on 3rd position in its group i.e. 2nd group.

And chlorine comes at last in its group i.e. 17 group.

As ionisation enthalpy $\bold{decreases}$ down the group due to increase in size.

Therefore,

Calcium has the third highest ionisation enthalpy in its group.

So, $\bold{option \ A)}$ Calcium Chloride is correct.