Electron affinities of two elements A and B are given as follows : A = 3.79 electron volts and B = 3.56

Question

(i) Electron affinities of two elements A and B are given as follows : A = 3.79 electron volts and B = 3.56 electron volts Which of them will ionize more easily and why ? 

(ii) A, B and C are the elements or a Dobereiner’s triad. If the atomic mass of A is 7 and that of C is 39, what should be the atomic mass of B ? 

(iii) Account for the difference in size of Fe³⁺ as Fe²⁺ = 0.76A and Fe³⁺ = 0.64Å. 

Answer 1

(i) A will ionize more easily than B because more is the electron affinity of an element, the more will be the tendency to accept electrons and hence get ionized easily. 

(ii) 

(iii) The size of Fe³⁺ (0.64Å) is smaller than the size of Fe²⁺ (0.76Å) because the effective nuclear charge per electron increases. The electron are more strongly attracted and pulled towards the nucleus. This causes decrease in the size of the Fe³⁺ ion.