Question

Select the ion/atom from each set with the largest ionic/atomic radius.

Rb^+1 or Br^-1

Y^+1 or Sc^+1

Al or S

Answer 1

In a group the ionic radii of ions increases as we go down because new shells are involved.

The radius decreases as we go towards right in a period. This decreases is seen because the electrons are being added to the same shell and as the electron increases the proton will also increase in the nucleus. So the attractive force will also increase and this results in decrease in the ionic radii.

a. Rb+1 and Br-1

Both have same number of electrons. But Rb+1 has more number of protons so more attractive force. So Rb+1 has smaller ionic radius than that of Br-1

b. Y+1 and Sc+1

Both lies in the same group. In a group as we go down, the ionic radii increases. So Y+1 is larger than Sc+1.

c. Al or S

Both lies in the same period. But Sulfur has more protons and electrons, so there will be more attractive forces. So Al will have larger atomic radius than that of S.