Question

Which of the following is methanide?
(A) $B{e}_{2}C$
(B) $Ca{C}_2$
(C) $M{n}_{3}C$
(D) $M{g}_3{C}_2$

Answer 1

Hint Before solving this question, we should have prior knowledge about carbides. The carbides are the compounds which contain carbon along with the other less electronegative metals. Methanides are carbides. Methanides are formed at very high temperatures around above 1500 degree centigrade.

Complete answer:
A methanide is a carbide having $C^{4-}$ carbon centre. We have to find out the particular carbon centre type in the given options. Methanides are carbides. Methanides are formed at very high temperatures around above 1500 degree centigrade. This varies for different metals and metal oxides. The metal atom when combined with the carbon atom forms a carbide.
Carbides are stable compounds and they have high melting points. We can divide carbides on the basis of their nature of chemical bonding. The types of chemical carbides are covalent carbides, interstitial carbides and salt like carbides.
Among the following options, only $B{e}_{2}C$ is a methanide. It has $C^{4-}$ carbon centre. All other options are not methanide as for example $Ca{C}_2$ does not have $C^{4-}$ carbon centre, it is of ${C_2}^{2-}$ type and known as acetylide.

Hence, the correct answer is option (A) i.e. $B{e}_{2}C$ is a methanide.

Note: Here most of the carbides which are given in the option are ionic carbides. These carbides are also known as salt-like or saline carbides. In the group 14 elements aluminium is the only element which forms carbide. The salt like carbides includes methanide, acetylides and allylides. Allylides are also known as sesqui carbides.