General Properties of Halogens

The group name thus emphasizes the facility with which these atoms form ionic compounds with a formal negative unit charge on the halo-gen (X ). Equally well known are covalent halogen compounds with bonds of the type R-X. In fact with the exception of helium, neon and argon all elements in the Periodic Table can form halogen compounds of some kind. 

In comprehensive treatments of the chemistry of the halogens the properties of fluorine compounds are sufficiently different to motivate a separate chapter. A similar distinction is also practical in a discussion of manifestations of nuclear properties of the halogens, since all stable isotopes of chlorine, bromine and iodine have 

In Table 1.1 we have collected some atomic and nuclear properties of the halogens, fluorine being included for completeness and comparison. To stress the ambiguity of some properties such as electronegativity and ionic radius we have listed values from different authors - the original articles should be consulted for an account of the underlying criteria and definitions. 

X will be used throughout as a general notation for a halogen. 

Isotopic ratio of nuclear electric quadrupole moments - 1.26879 1.19707 - (i) 

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