Question

A, B, C are three elements with atomic numbers, Z-1, Z and Z+1 respectively. B is an inert gas. Which of the three has least value of ionisation energy?

• A. A
• B. B
• C. C
• D. Cannot be predicted

Answer 1

The correct option is C C

The element having atomic number one greater than inert gases is alkali metal of the next period and one less than inert gases is halogen of the same period. Thus 'C' is an alkali metal and hence has the lowest ionization energy.

Hence the correct option is 'C'.