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What is Carbide?

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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.

Carbide Formula

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. 

Carbide 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

  • It can be produced by heating metal oxide with carbon.

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. 

  1. Ionic carbides

  2. Covalent carbides

  3. Interstitial carbides

  4. 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.

FAQ (Frequently Asked Questions)

1. Explain the carbide chemical formula?

The carbide chemical formula is C2-2. It shows that carbide is a negative ion. It carries two negative charges. Therefore, it is called a dianionic form of carbon. The carbide anion contains two carbon atoms. These atoms are bonded together with the three covalent bonds. From these three covalent bonds, one is sigma and the other two are pi-bonds. The pi-bonds are formed by the lateral overlapping and the sigma bond is formed by the head-on overlapping. The sigma bond is stronger than the pi bonds. The total or net bond strength of the carbide ion is high, due to the triple bond.

2. What are the different types of carbides?

1. Ionic Carbide - These types of carbides are also known as saline carbides. These are formed by the fusion of electropositive metals and carbide ions.

2. Covalent Carbide - These types of carbide are formed by the fusion of carbide ions with elements with similar electronegativity. Boron and silicon have similar electronegativity as that of carbon. Therefore, these two elements form covalent carbide.

3. Interstitial Carbide - Interstitial carbides are the carbides of the group-IV, -V, and VI transition metals of the periodic table. Interstitial carbides are formed so that the carbon atoms of the carbide ion get fit into the octahedral interstices of a close-packed metal lattice.

4. Intermediate Transition Metal Carbide - This type of carbide is formed by the fusion of transition elements (having a similar size as that of carbon) and carbide ions.