Covalent Bonding in Carbon CompoundsConsider the formation of some other molecules which are formed by different types of atoms.
- Methane (CH4): Carbon has four electrons in its valence shell. It requires four electrons to complete its octet. Therefore, four hydrogen atoms share one electron each with carbon. Thus each hydrogen atom completes its valence shell with two electrons and the carbon atoms with eight electrons.
- Ethyne (C2H2): In ethyne there are two carbon atoms with four valence electrons each. But they are linked to only two hydrogen atoms, one with each carbon atom. Only two single covalent bonds will be formed since hydrogen can share only one electron of carbon. So triple covalent bond is formed from the six remaining electrons of the two carbon atoms.
Thus, an ethyne molecule contains two single carbon-hydrogen covalent bonds and one triple covalent bond between two carbon atoms.
- Ethene (C2H4): In ethane the two carbon atoms are linked to two hydrogen atoms with two single covalent bonds and the two electrons of each carbon atom form a double bond between the two carbon atoms.
- Carbon tetrachloride (CCl4): Similar to methane molecule, carbon forms four single covalent bonds between carbon and chlorine.
The total number of electron pairs shared by a single atom in forming a covalent bond (may be single, double or triple covalent bond) to acquire its nearest noble gas configuration, is known as its covalence.
Characteristics of Covalent Compounds
- Covalent compounds do not conduct electricity. The types of covalent compounds which are discussed above, are bad conductors as they do not form ions in the molten state or when dissolved in water.
- Covalent compounds are generally insoluble (or sparingly soluble) in water. Covalent compounds are generally non-polar in nature so they are insoluble (or sparingly soluble) in water but are usually soluble in organic solvents like benzene, chloroform, etc.
- Covalent compounds have low melting and boiling points. Since the force of attraction between the covalent molecules is weak, these compounds have comparatively low melting and boiling points.
- Covalent compounds are generally volatile liquids or gases. Since the covalent compounds are made up of electrically neutral molecules and not ions, the force of attraction between the molecules is weaker than the ionic attraction in the ionic compounds and the compounds are, therefore, generally volatile liquids or gases.