Question

F, Cl and Br are the elements each having seven valence electrons. Which of these (i) has the largest atomic radius, (ii) is most reactive? Justify your answer stating reason for each.

Answer 1

i. F, Cl and Br all are in the same group and thus have the same effective nuclear charge. Br has

the largest atomic radius among all because it uses the largest number of electron energy levels since the

valence electrons are placed in larger orbitals i.e. the principal quantum number increases on going down the

group.

ii. Fluorine is the most reactive since it has the greatest tendency to gain electrons because it has a higher

effective nuclear charge and uses fewer energy levels than Br and Cl.

Answer 2

(i) Br has the largest atomic radius. In a group, the size of an atom increases as one proceeds from top to bottom. This is due to the successive addition of shells.

(ii) Fluorine is the most reactive.The chemical reactivity of non-metals decreases on going down the group as it depends upon the tendency to gain electrons, which decreases down the group.