Electron affinity & variation with group and periods

Electron affinity:

electron affinity may be defined as amount of energy released when an electron is added to neutral gaseous atom to form gaseous anion.

X(g) + 1e^- → X(g) ^-

Variation of electron affinity in group:
Electron afinity is decrease from top to buttom in a group. because as atmic size increase attraction for extra electron decrease.

Variation of electron affinity in periods: Electron affinity is increase from left to right in a periods. because as effective nuclear charge increase attraction for extra electron increase.

# electron affinity first is always +ve.
# successive electron affinity is always -ve.

O + 1e^- →O^-
neutral & - ve charge molecule no large amount of energy require and both when mix it defuse .so electron affinity of first is always +ve.

O^- + 1e^- →O^2-
-ve & -ve charge molecule greater repulsion between than so more energy require to mix together each other so E. A of successive is always -ve.

Question 1

Successive electron affinity has -ve value?
ans

O + 1e^- →O^-
neutral & - ve charge molecule no large amount of energy require and both when mix it defuse .so electron affinity of first is always +ve.

O^- + 1e^- →O^2-
-ve & -ve charge molecule greater repulsion between than so more energy require to mix together each other so E. A of successive is always -ve.

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