Nitrogen ionic crystal radius

The above speculation [21] may be extended to include the related quaternary ammonium compounds such as xylocholine (XXXIX). It is probable that the volumes of the guanidinium ion and the trimethylammonium group are similar. The ionic radius of the guanidinium ion (IX) is about 3A the ionic radius of the tetramethylammonium ion has been estimated [300] to be 3-4A, although rather smaller values have also been proposed [301-303]. Crystallographic analyses of muscarine iodide [304], choline chloride [305] and acetylcholine bromide [306] have revealed that the carbon to nitrogen distance is about l-SA, and that a hydrogen bond (C-H-0 distance 2-87-3 07A) exists in the crystals of these compounds. 

The type of lattice is not always determined by the radius ratio. For example, the ratio of the ionic radii in GaS and GdS is identical (0 53) but nevertheless GaS crystallizes in a sodium chloride lattice and GdS in a zinc sulphide type. Similar behaviour is observed with the corresponding tellurides. For sulphur, nitrogen and their analogues where the valency state of nitrogen is... 

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