The minimum amount of energy required to Cloze (1): JXUwMDNmJXUwMDA2JXUwMDA4JXUwMDA3 /acquire an extra electron by  an Cloze (2): JXUwMDM5JXUwMDE1JXUwMDFiJXUwMDAy of element in its gaseous state is called  1st electron affinity.

The SI unit of electron affinity is Cloze (3): JXUwMDMzJXUwMDAyJXUwMDA1JXUwMDAzJXUwMDA1JXUwMDA1JXUwMDFhJXUwMDE5JXUwMDA5JXUw MDE2 per mole/kJmole-1 . Electron affinity depend on atomic radius.

The higher the atomic radius, the Cloze (4): JXUwMDM0JXUwMDA5JXUwMDE2JXUwMDAw effective the nuclear attraction on outer energy level electrons and thus the lower the Cloze (5): JXUwMDNkJXUwMDA5JXUwMDA5JXUwMDA2JXUwMDE3JXUwMDA2JXUwMDFkJXUwMDAx affinity.

For halogens the 1st electron affinity Cloze (6): JXUwMDNjJXUwMDAxJXUwMDA2JXUwMDExJXUwMDE3JXUwMDA0JXUwMDEyJXUwMDE2 down the group as the atomic radius increase and the effective nuclear attraction on outer energy level electrons decrease.

 Due to its Cloze (7): JXUwMDJiJXUwMDFlJXUwMDBjJXUwMDBkJXUwMDAw size/atomic radius Fluorine shows exceptionally low electron affinity.

This is because a lot of energy is required to overcome the high Cloze (8): JXUwMDJhJXUwMDE3JXUwMDE1JXUwMDA1JXUwMDE5JXUwMDFmJXUwMDFhJXUwMDA2JXUwMDAx of the existing and incoming electrons.

Cloze (9): JXUwMDExJXUwMDI2JXUwMDAxJXUwMDA3JXUwMDEzJXUwMDFiJXUwMDE1JXUwMDFkJXUwMDA2JXUw MDAx energy is the energy required to lose/donate an electron in an atom of an element in its Cloze (10): JXUwMDNmJXUwMDA2JXUwMDEyJXUwMDE2JXUwMDBhJXUwMDFhJXUwMDA2 state while electron affinity is the energy required to gain/acquire extra electron by an atom of an element in its gaseous state.