Question

Explain the energy changes involved in the formation of $F^{-}$ and $O^{2-}$ from their respective atoms.

Answer 1

1. Anion: A negatively charged particle formed when an atom gains electrons.

Example: $F+e^{-}\to F^{-}$

2.Fluorine is an unstable atom with $1s^{2}2s^{2}2p^5$ configuration, on gaining 1 electron it attains Ne configuration $1s^{2}2s^{2}2p^6$ which is stable.

3.When an electron is added to F, it releases its free energy and attains minimum energy condition. Hence, the energy is released called electron gain enthalpy or electron affinity.(E.A).

4.Oxygen is an unstable atom with $1s^{2}2s^{2}2p^4$ configuration, on gaining 1 electron it attains $1s^{2}2s^{2}2p^5$ configuration which is still unstable but it loses some of its free energy and it is called first Electron affinity.

$O+e^{-}\to O^{-}$;$E.A_1$;$(∆=-ve)$

5.Addition of second electron to the uninegative ion requires energy to overcome the repulsive forces caused by the extra electron in the valence shell and attains $1s^{2}2s^{2}2p^6$ configuration. The energy required to add the second electron is called second electron affinity.

$O^{-}+e^{-}\to O^{-2}$;$E.A_2$;$(∆=+ve)$