Question

The ionisation energies of elements U, V, W and X are 2480,550,950 and 1690 kJ mol^-1 respectively. Which of the statements about these elements are correct? 

(i) V is a reactive metal. 

(ii) X is a reactive non-metal. 

(iii) U is a noble gas. 

(A) (i) and (ii) only 

(B) (ii) and (iii) only 

(C) (i) and (iii) only 

(D) (i), (ii) and (iii)

Answer 1

Correct option  (D) (i), (ii) and (iii)

Explanation:

As we move across a period from left to right, ionisation energy increases due to decrease in atomic size. V is a reactive alkali metal which has low value of first ionisation energy and loses one electron easily to form monovalent cation.

X is a reactive non-metal which has high value of first ionisation energy thus, it prefers to gain electron rather than losing. U having very high value of ionisation energy is a noble gas which has stable, completely filled electronic configuration and is chemically inert.