Question

The first ionisation energy (IE₁) and second ionisation energy (IE₂) of elements X, Y and Z are given below.

Element	IE1 (KJ mol-1)	IE2 (KJ mol-1)
X	2370	5250
Y	522	7298
Z	1680	3381

Which one of the above elements is the most reactive metal, the least reactive metal and a noble gas?

Answer 1

Noble gases: 

Ioniation energy ranging from 2372 KJmol^-1 to 1037 kJmol^-1 . For element X, the IE₁ value is in the range of noble gas, moreover for this element both IE₁ and IE₂ are higher and hence X is the noble gas. For Y, the first ionisation energy is low and second ionisation energy is very high and hence Y is most reactive metal. For Z, both IE₁ and IE₂ are higher and hence it is least reactive.