Question

The arrangement elements according to increasing reactivity for group 1 and 17 are given:

For group 1: Li < Na < K < Rb < CsLi<Na<K<Rb<Cs

For group 17: F > Cl > Br > IF>Cl>Br>I

​

Answer 1

Explanation:

Ans.) For group 1

There is only 1 valance electron in the elements of group 1. So, their tendency is to expel this electron in order to achieve stable inert gas configuration. As we move down in group 1 the ionization enthalpies of the elements decreases. Thus, less energy will be required to expel the valence electron. As a result reactivity of elements increases as we move down in group 1.

For group 17

In the elements of group 17, there is requirement of only 1 electron in order to achieve stable inert gas configuration. So, their tendency is to gain this 1 electron. As we move down in group 17 the ionization enthalpies of the elements increases. Thus, more energy will be required to expel the valence electron. As a result reactivity of elements decreases as we move down in group 17.