Question

A trend common to both group I and VII elements in the periodic table as atomic number increases is :

• A. atomic radius increases
• B. oxidising power increases
• C. reactivity with water increases
• D. None of the above

Answer 1

The correct option is A atomic radius increases

a. As we move down the group number of shells increases and hence atomic radius increases down the group. So it is correct.

Oxidizing power means to oxidise other species and itself gets reduced. For group 1, both bond energies and electron affinities decrease down the group as the nuclear pull on the outer electrons decrease. So , oxidising ability decreases down the group as the nuclear pull on the outer electrons decreases down the group.

Again, reactivity for group 1 metals with water decreases as charge density on the atom decreases.

For group 17 , down the group halogens is involved in oxidising something in solution, the halogen ends up as halide ions. Fluorine is such a powerful oxidising agent that you can't reasonably do solution reactions with it. So as we go down the group , oxidising ability falls.

Again , for group 17 , in fluorine as it is too strong an oxidising agent. Fluorine oxidises water to oxygen.As you go down the Group, the ions become less attractive to water molecules as they get bigger. So , reactivity with water decreases for group 17