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What Is a Covalent Bond?

A covalent bond is formed when two or more non‑metal atoms share one or more pairs of valence electrons, creating a stable, directional connection. Breaking such a bond requires significant energy—typically between 50 and 200 kcal/mol—reflecting its strength and the stability it confers to the molecule.

Key Features of Covalent Bonds

• Only non‑metals (or metalloids) with similar electronegativities form covalent links.
• Electrons are shared within the outermost shells, giving the atoms a fixed spatial orientation.
• Polarity depends on electronegativity differences: equal sharing yields a non‑polar covalent bond; unequal sharing produces a polar covalent bond.
• Because of the low polarity and the strong directional nature, molecules with covalent bonds often have low melting and boiling points, remaining gases or liquids at room temperature.

Common Examples of Covalent Molecules

• Methane (CH₄) – a non‑polar molecule where carbon shares four equivalent electron pairs with hydrogen.
• Hydrochloric acid (HCl) – a polar covalent bond; chlorine’s higher electronegativity pulls the shared pair toward itself.
• Water (H₂O) – a classic polar covalent molecule; oxygen’s stronger pull creates a dipole moment, giving water its unique properties.
• Ammonia (NH₃) – a polar covalent compound with a trigonal pyramidal geometry.

Contrast With Ionic Bonds

In an ionic bond, a metal donates one or more electrons to a non‑metal, producing oppositely charged ions that attract each other. Everyday examples include table salt (NaCl), fluoride toothpaste (NaF), rust (Fe₂O₃), and antacid calcium hydroxide (Ca(OH)₂).