Consider the following neutral electron configurations in which n has a constant value. Which configuration would belong to the element with the most negative electron affinity, E-ea?

a. ns^2

b. ns^2 np^2

c. ns^2 np^5

d. ns^2 np^6

ns^2 np^5

Explanation:

Now let us try to analyse our options carefully in order to make an informed decision about the correct answer.

The answer cannot be ns^2 since any atom with this configuration must be a metal in group 2. Secondly, ns^2 np^2 is an element in group 14. Again, this specie cannot have the most negative electron affinity. The atom whose outermost electron configuration is ns^2 np^6 must be a noble gas since the outermost shell possesses eight electrons. This cannot be the answer we are seeking for.

However, an outermost electron configuration of ns^2 np^5 will apply to a halogen. Halogens have a very negative electron affinity. Hence a specie with this electron configuration must have the most negative electron affinity among the options.