Short Answer:

Nonmetals form covalent compounds because they have high electronegativity and lack free electrons, making it difficult for them to lose electrons like metals. To achieve a stable electron configuration, nonmetals share electrons with other nonmetals, forming covalent bonds.

For example, oxygen forms water (H₂O) by sharing electrons with hydrogen, and chlorine forms Cl₂ by sharing electrons with another chlorine atom. Covalent bonding allows nonmetals to achieve a full outer shell while maintaining chemical stability.

Detailed Explanation:

Formation of Covalent Compounds by Nonmetals

Nonmetals are elements that are located on the right-hand side of the periodic table. They typically have 4 to 8 valence electrons and high electronegativity, meaning they strongly attract electrons. Because nonmetals cannot easily lose electrons to form positive ions, they tend to share electrons with other nonmetals to achieve a stable octet configuration. This sharing of electrons forms covalent bonds, which are the foundation of covalent compounds.

Reasons Nonmetals Form Covalent Compounds

1. High Electronegativity:
   • Nonmetals attract electrons strongly.
   • Rather than giving up electrons (which is difficult), they share them with other atoms.
2. Electron Deficiency:
   • Nonmetals need to complete their outermost electron shell (usually 8 electrons).
   • Covalent bonding allows them to achieve stability without losing electrons.
3. Similar Reactivity with Other Nonmetals:
   • When two nonmetals react, neither can form positive ions easily.
   • Sharing electrons creates a mutually stable compound.
4. Energy Stability:
   • Covalent bonds release energy and make the resulting molecule more stable than individual atoms.

Examples of Covalent Compounds

1. Water (H₂O):
   • Oxygen shares electrons with two hydrogen atoms.
   • Each atom achieves a complete outer shell.
2. Carbon Dioxide (CO₂):
   • Carbon shares electrons with two oxygen atoms.
   • Double covalent bonds form, giving stable electron configurations.
3. Oxygen Gas (O₂):
   • Two oxygen atoms share electrons in a double bond.
4. Nitrogen Gas (N₂):
   • Two nitrogen atoms share three pairs of electrons forming a triple bond, making it very stable.
5. Hydrogen Chloride (HCl):
   • Hydrogen shares one electron with chlorine, forming a single covalent bond.

Properties of Covalent Compounds

1. Low Melting and Boiling Points:
   • Weak intermolecular forces between molecules result in low melting and boiling points.
2. Poor Conductors of Electricity:
   • Covalent compounds do not have free electrons or ions, so they are insulators.
3. Brittle Nature in Solids:
   • Solid covalent compounds are usually soft or brittle.
4. Solubility:
   • Many covalent compounds are soluble in organic solvents but insoluble in water (except polar molecules like H₂O).

Importance of Covalent Compounds

• Biological Molecules: Proteins, carbohydrates, fats, and nucleic acids are covalent compounds.
• Industrial Use: Plastics, dyes, medicines, and chemical products often involve covalent compounds.
• Environmental Role: Oxygen, nitrogen, and carbon dioxide are covalent molecules essential for life and ecological balance.

Summary

Nonmetals form covalent compounds due to their high electronegativity, inability to lose electrons, and tendency to share electrons to achieve a stable octet. Covalent bonding allows them to form stable, energy-efficient molecules with other nonmetals.

Conclusion:

The formation of covalent compounds by nonmetals is a natural consequence of their electron configuration and chemical properties. By sharing electrons, nonmetals achieve stability and form molecules that are essential in biological systems, industrial applications, and environmental processes. Covalent bonding is therefore a fundamental concept in understanding nonmetal chemistry.