Carbide is the most common term used in inorganic chemistry and organic chemistry. Let’s come to the main question: what is carbide? The carbide is a chemical compound composed of carbon and metal or semi-metallic elements. It exists in an ionic form. The carbide group is attached to the metal or semi-metallic element with the ionic or covalent bond. The Carbide symbol is represented as C2-2. It represents that carbide ions are made up of two carbon atoms.
The carbide formula is C2-2. The Carbide formula represents that the carbide exists in a dianionic form state. On looking at the carbide ion formula you can not get an idea about the lone pairs and the hybridisation. For that, you need to have knowledge of the carbon electronic structure and its structure.
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In carbide structure, two carbon atoms are attached to each other with the three covalent bonds. From these three covalent bonds, two bonds are pi-bonds. These pi-bonds are formed by the lateral overlapping of the p-orbitals. Another bond is the sigma bond, which is formed by the head-on overlapping of the s-orbitals. The hybridization exhibited by the carbon in the carbide structure is sp. Each carbon carries one lone pair on it.
General Properties of Carbides
Carbides generally have a very high melting point.
Carbides are good conductors of electricity.
Carbides are good conductors of heat.
Carbides compounds generally possess lustre.
Preparation methods of Carbides
CaO + 3C → CaC2 + CO
C2H2 + 2 Li → LiC2 + H2
Types of Carbide
The carbides can be divided into various types, depending on the nature of the bond formed between the carbide ion and the metal or semi-metallic element.
Intermediate transition metal carbides
Ionic Carbide - Ionic carbides are formed by the combination of highly electropositive elements like alkali metals or alkaline earth metals and carbide ions. These ions are attracted to each other by the strong electrostatic force. This type of ionic carbide exhibits a high electronegativity difference. Examples of ionic carbides are calcium carbide.
Covalent Carbides - Covalent carbides are formed by the combination of low electropositive elements like silicon and boron. They exhibit low electronegativity difference. Some examples of covalent carbides are: Boron carbide and silicon carbide or commonly known as carborundum (SiC).
Interstitial Carbides - Interstitial carbides are composed of large transition metals and carbide molecules. The carbide ions occupy the interstitial sites of the closed packed metal lattice.
Intermediate Transition Metal Carbide - Intermediate transition metal carbide is composed of transition metal and the carbide ion. The size of the transition metal and the carbide ion is similar in this type of carbide. Few examples of intermediate carbides are carbides of Iron like cementite Fe3C.
Did You Know?
Carbides like carborundum (SiC), tungsten carbide are very hard in nature. These Carbides fall just under the diamond in terms of hardness.
Some Carbides are used in cutting hard materials.
Boron carbide is the hardest synthetic substance.
Silicon carbide occurs in nature.
Carbides are used in the metallurgy process.
Carbiding or carburizing is the process of producing carbide coating on a metal piece. This process is used in the metallurgy process.