Systematics reduced melting point

A study of table 3.04 shows, as of course follows immediately from equation (3.02), that lattice energy increases as interionic distance decreases Other properties also show a systematic dependence on this distance. Thus, as the distance between the ions increases and the lattice energy is reduced the melting point and hardness of the crystals fall progressively, while conversely the coefficients of thermal expansion and of compressibility increase. 

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