Name: Periods in the Modern Periodic Table
Uploaded: 2019-07-19
Duration: 5 min 31 s
Description: The general characteristics of periods are identified by its total number of shells in an atom or period number. The electronic configuration of an element d...

Question

Explain the term electron affinity. Mention the units in which they are measured. How do they generally vary (i) in a group and (ii) in a period?

Accepted Answer

The electron affinity of an atom is defined as the amount of energy released when an electron is added to a neutral atom in the gaseous state to form a negative ion.

The unit used to measure electron affinity is $kJ / mol$ .

(i) On moving from top to bottom in a group, electron affinity decreases because the number of shells increases due to which all incoming electrons are added to the new shells and the attraction between the electron and the nucleus decreases hence decrease in nuclear charge. Thus, electron affinity decreases down the group.

(ii) On moving from left to right in a period electron affinity increases due to the increase in nuclear charge. From left to right the atomic radius decreases and all incoming electrons are added to the same shell hence the attraction between the electron and the nucleus increases. Therefore, the size of the atom decreases. Thus, elements can easily accept the electrons and therefore electron affinity increases.

Explain the term electron affinity. Mention the units in which they are measured. How do they generally vary (i) in a group and (ii) in a period?

Important Questions on Periodic Classification of Elements

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