Germanium, elemental metal halides

All Group IV elements form tetrachlorides, MX4, which are predominantly tetrahedral and covalent. Germanium, tin and lead also form dichlorides, these becoming increasingly ionic in character as the atomic weight of the Group IV element increases and the element becomes more metallic. Carbon and silicon form catenated halides which have properties similar to their tetrahalides. 

The metal-nonmetal line passes through the heart of the group, with carbon being a bona fide nonmetal and lead a bona fide metal. In between are two metalloids (silicon and germanium) and a borderline metal (tin). The progression in the acid-base character of the oxides of the elements further emphasizes the trend from nonmetal to metal. The formulas of the oxides and halides show the increasing importance of the +2 oxidation state down the group, and this is reinforced by a consideration of standard reduction potentials. 

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