Halogens Group electron affinities

Halogens, the elements in Group 17 of the periodic table, have the largest electron affinities of all the elements, so halogen atoms (a n readily accept electrons to produce halide anions (a a. This allows halogens to react with many metals to form binary compounds, called halides, which contain metal cations and halide anions. Examples include NaCl (chloride anion), Cap2 (fluoride anion), AgBr (bromide anion), and KI (iodide anion). 

The electron affinities for the halogens are the highest of any group of elements. 

For non-metal elements, such as the halogens (group 7), the concept of electron affinity is far more useful than ionisation energy. These elements form negative ions in ionic compounds. 

As the size of the halogen atom increases, the force of attraction between the nucleus of the atom and the incoming electron decreases. Therefore, the first electron affinities become less exothermic down group 7. 

Symbol Br atomic number 35 atomic weight 79.904 a halogen group element electron affinity 3.36359 eV electronegativity 2.8 electron configuration [Ar] 3di°4s24p5 most stable valence states -1 and -i-5, less stable valence states -1-1 and -i-3 a diatomic molecule (Br2) in liquid and vapor states over a wide range of temperature two stable isotopes, Br-79 (50.57%) and Br-81 (49.43%). 

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