ELECTRON AFFINITY
It is defined as the energy releases on adding an electron to neutral,isolated gaseous atom to change it into a single negatively charged ion(anion) .
Let x be any atom
x+e - --> x- +energy (This energy is called electron affinity)
FACTORS EFFECTING ELECTRON AFFINITY
(i)Atomic size : The smaller the atomic size greater is electron affinity and vice versa.
Smaller atoms have strong force of attraction between the valence shell and the nucleus . So,more energy is released on adding a electron to its valence shell.
(ii)Nuclear charge : The greater is the nuclear charge greater is the electron affinity.
More is the nuclear charge more is the force of attraction between the valence shell and the nucleus.So,more energy is released on adding a electron to its valence shell.
(iii)Configuration: More stable the configuration is lesser is its tendency to attract electron and lesser is electron affinity.
More is the nuclear charge more is the force of attraction between the valence shell and the nucleus.So,more energy is released on adding a electron to its valence shell.
(iii)Configuration: More stable the configuration is lesser is its tendency to attract electron and lesser is electron affinity.
TRENDS IN PERIODIC TABLE:
Across the period:
Across the period the atomic size decreases so there is a increase in electron affinity.
Down the group:
Down the group the atomic size increases so there is a decrease in electron affinity.
Down the group:
Down the group the atomic size increases so there is a decrease in electron affinity.
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