Question

How many unpaired electrons does the second excited state of halogens (= Cl, Br and I) have?

• A. 5 unpaired electrons
• B. 7 unpaired electrons
• C. There is no second excitation possible for Cl, Br and I.
• D. None of the above

Answer 1

The correct option is A 5 unpaired electrons

Following are the different electronic configurations of halogens:
Ground state electronic configuration is $n{s}^{2}n{p}^{5}n{d}^0$
First excited state electronic configuration is $n{s}^{2}n{p}^{4}n{d}^1$
Second excited state electronic configuration is $n{s}^{2}n{p}^{3}n{d}^2$
Third excited state electronic configuration is $n{s}^{1}n{p}^{3}n{d}^3$

We can clearly see from the electronic configuration of the second excited state that the number of unpaired electrons are 5.