A) O changes into \[{{O}^{-}}\]
B) \[{{O}^{-}}\] changes into \[{{O}^{2-}}\]
C) O changes into \[{{O}^{+}}\]
D) electron affinity is always negative
Correct Answer: B
Solution :
Electron affinity may be defined as The amount of energy which is released when an extra electron enter in the valence orbital of an isolated neutral atom of a negative ion. It is an exothermic process. \[O+{{e}^{-}}\xrightarrow{{}}{{O}^{-}}+\] energy EA = - 141 k J \[mo{{l}^{-1}}\] but when \[{{O}^{-}}\] changes into \[{{O}^{2-}}\] the change is endothermic and the electron affinity is positive because the electron is° being added against the electrostatic repulsion existing between the negatively charged electron and negatively charge ion. Hence, it needs energy to accept the electron. \[{{O}^{-}}+{{e}^{-}}\xrightarrow{{}}{{O}^{2-}}\] E A = 702 kJ \[mo{{l}^{-1}}\]
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