All halogen atoms have Cloze (1): monovalentelectron affinitylessexceptionincreaseatomicsevengainrepulsion JXUwMDJiJXUwMDE2JXUwMDEzJXUwMDEzJXUwMDBi electrons in the outer energy level. They acquire/ Cloze (2): monovalentelectron affinitylessexceptionincreaseatomicsevengainrepulsion JXUwMDNmJXUwMDA2JXUwMDA4JXUwMDA3 one electron in the outer energy level to be stable. They therefore are therefore Cloze (3): monovalentelectron affinitylessexceptionincreaseatomicsevengainrepulsion JXUwMDM1JXUwMDAyJXUwMDAxJXUwMDAxJXUwMDE5JXUwMDE3JXUwMDBkJXUwMDA5JXUwMDBiJXUwMDFh . They exist in oxidation state X- The number of energy levels increases down the group from Fluorine   to Astatine. The more the number of energy levels the bigger/larger the Cloze (4): monovalentelectron affinitylessexceptionincreaseatomicsevengainrepulsion JXUwMDM5JXUwMDE1JXUwMDFiJXUwMDAyJXUwMDA0JXUwMDBh size. e.g.The atomic size/radius of Chlorine is bigger/larger than that of Fluorine because Chlorine has more/3 energy levels than Fluorine (2 energy levels). Atomic radius and ionic radius of Halogens Cloze (5): monovalentelectron affinitylessexceptionincreaseatomicsevengainrepulsion JXUwMDMxJXUwMDA3JXUwMDBkJXUwMDExJXUwMDE3JXUwMDA0JXUwMDEyJXUwMDE2 down the group as the number of energy levels increases.

The minimum amount of energy required to gain/acquire an extra electron by  an atom of element in its gaseous state is called  1st Cloze (6): monovalentelectron affinitylessexceptionincreaseatomicsevengainrepulsion JXUwMDNkJXUwMDA5JXUwMDA5JXUwMDA2JXUwMDE3JXUwMDA2JXUwMDFkJXUwMDAxJXUwMDRlJXUwMDQxJXUwMDA3JXUwMDAwJXUwMDBmJXUwMDA3JXUwMDA3JXUwMDFkJXUwMDBk . The SI unit of electron affinity is kilojoules per mole/kJmole-1 . Electron affinity depend on atomic radius. The higher the atomic radius, the Cloze (7): monovalentelectron affinitylessexceptionincreaseatomicsevengainrepulsion JXUwMDM0JXUwMDA5JXUwMDE2JXUwMDAw effective the nuclear attraction on outer energy level electrons and thus the lower the electron affinity. For halogens the 1st electron affinity decrease down the group as the atomic radius increase and the effective nuclear attraction on outer energy level electrons decrease. Due to its small size/atomic radius Fluorine shows Cloze (8): monovalentelectron affinitylessexceptionincreaseatomicsevengainrepulsion JXUwMDNkJXUwMDFkJXUwMDFiJXUwMDA2JXUwMDE1JXUwMDA0JXUwMDFkJXUwMDA2JXUwMDAx ally low electron affinity. This is because a lot of energy is required to overcome the high Cloze (9): monovalentelectron affinitylessexceptionincreaseatomicsevengainrepulsion JXUwMDJhJXUwMDE3JXUwMDE1JXUwMDA1JXUwMDE5JXUwMDFmJXUwMDFhJXUwMDA2JXUwMDAx of the existing and incoming electrons.