THE OTHER GROUP 4A ELEMENTS Si, Ge, Sn, AND Pb

The carbide ion is a very strong base that reacts with water to form acetylene (H —C = C —H)  

Interstitial carbides are formed by many transition metals. The carbon atoms occupy open spaces (interstices) between the metal atoms in a manner analogous to the interstitial hydrides (Section 22.2). This process generally makes the metal harder. Tungsten carbide, for example, is very hard and very heat-resistant and, thus, used to make cutting tools. 

Covalent carbides are formed by boron and silicon. Silicon carbide (SiC), known as Carborundum , is used as an abrasive and in cutting tools. Almost as hard as diamond. Sic has a diamondlike structure with alternating Si and C atoms. 

Hydrogen cyanide, HCN, is an extremely toxic gas that famously has the odor of bitter almonds. It is produced by the reaction of a cj anide salt, such as NaCN, with an acid. Aqueous solutions of HCN are known as hydrocyanic acid. Neutralization with a base produces cyanide salts, which are used in the manufacture of several plastics, including nylon and Orion . The CN ion forms stable complexes with most transition metals. (Section 17.5) 

Carbon disulfide, CS2, is an important industrial solvent for waxes, greases, celluloses, and other nonpolar substances. It is a colorless, volatile liquid (bp 46.3 °C). The vapor is very poisonous and highly flammable. 

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