CBSE · Class 10 · Science · Carbon and its CompoundsExplain the formation of covalent bonds in carbon compounds with the help of suitable examples. Also, explain why carbon forms covalent bonds instead of ionic bonds by losing or gaining electrons.

Introduction to Carbon Bonding\nCarbon is a unique element that forms a vast number of compounds. The atomic number of carbon is 6, which means it has 6 electrons distributed in its shells as 2 in the K-shell and 4 in the L-shell. Therefore, carbon has 4 valence electrons in its outermost shell and needs 4 more electrons to achieve a stable noble gas configuration (octet).

Why Carbon Forms Covalent Bonds\nCarbon cannot form ionic bonds due to the following energetic reasons:

• Gain of 4 electrons: If carbon were to gain 4 electrons to form a $C^{4-}$ anion, it would be difficult for the nucleus with 6 protons to hold onto 10 electrons, making the system highly unstable.
• Loss of 4 electrons: If carbon were to lose 4 electrons to form a $C^{4+}$ cation, it would require a massive amount of energy to remove four electrons from the valence shell, leaving behind a carbon cation with 6 protons holding onto only 2 electrons.
• Sharing of electrons: To overcome these energy barriers, carbon achieves stability by sharing its four valence electrons with other carbon atoms or atoms of other elements such as hydrogen, oxygen, nitrogen, and chlorine. This type of bonding through the sharing of electron pairs is known as a covalent bond.

Examples of Covalent Bonding

1. Formation of Methane ($CH_4$): Carbon shares its four valence electrons with four hydrogen atoms, each contributing one electron. This results in four single covalent bonds, allowing both carbon and hydrogen to attain stable configurations.
2. Formation of Oxygen Molecule ($O_2$): Each oxygen atom has 6 valence electrons and needs 2 more to complete its octet. They share two pairs of electrons between them, forming a double covalent bond.
3. Formation of Nitrogen Molecule ($N_2$): Each nitrogen atom has 5 valence electrons and shares three pairs of electrons, forming a triple covalent bond.

Characteristics of Covalent Compounds

• They have low melting and boiling points because the intermolecular forces of attraction are weak.
• They are generally poor conductors of electricity since they do not contain charged ions.
• They are mostly insoluble in water but soluble in organic solvents.