Question

Part A

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 $E_ea$ ?

2s2

2s2 2p2

2s2 2p5

2s2 2p6

Part B

Arrange the following elements from greatest to least tendency to accept an electron.

Rank from greatest to least tendency to accept an electron. To rank items as equivalent, overlap them.

Sr Sn Rb Te I

Answer 1

Concepts and reason

This problem is based on the concept of electron affinity.

Electron affinity is the amount of energy which is released by an isolated gaseous neutral atom on addition of an extra electron in order to form a negative ion. Some elemental atoms have negative electron affinity whereas some atoms have positive electron affinity which depends on the configuration of the atom.

Fundamentals

Stable configurations have positive electron affinity as it is required to provide some energy in order to add one extra electron whereas unstable configuration have negative electron affinity because they convert to the stable electron configuration on accepting one extra electron.

Part A

Configurations which require one electron in order to form half-filled or partially filled orbitals have negative electron affinities because large amount of energy released on the addition of electrons as compared to the partially filled orbital configurations. Based on this fact, the given configurations have:

$2{s^2}$ has positive affinity.

$2{s^2}2{p^2}$ has negative affinity.

$2{s^2}2{p^5}$ has negative affinity.

$2{s^2}2{p^6}$ has positive affinity.

Part B

For the given elements, the valence shell configuration are as follows:

The valence shell electronic configuration Sr is $5{s^2}$ .

The valence shell electronic configuration Sn is $5{s^2},5{p^2}$ .

The valence shell electronic configuration Rb is $5{s^1}$ .

The valence shell electronic configuration Te is $5{s^2},5{p^4}$ .

The valence shell electronic configuration I is $5{s^2},5{p^5}$ .

Ans: Part A

Configuration having the most negative electron affinity is $2{s^2}2{p^5}$ .

Part B

The order of electron affinity from greatest tendency to accept electron the least tendency of accepting electron is given below:

I >Te >Sn >Rb >Sr