Covalently bonded compounds are formed when atoms share electrons to achieve a stable electron configuration, typically a full outer electron shell (octet rule).
Formation of Covalent Bonds
Covalent bonds arise because atoms don't have enough energy to completely transfer electrons (as in ionic bonding). Instead, they share electrons to fill their valence shells. This sharing creates a region of high electron density between the atoms, effectively holding them together.
- Sharing of Electrons: Atoms share one or more pairs of electrons to form a covalent bond. Each shared pair constitutes one covalent bond.
- Electronegativity Difference: Covalent bonds typically form between atoms with similar electronegativity values. If the electronegativity difference is too large, ionic bonding is favored.
- Stability: The shared electrons are attracted to the nuclei of both atoms, resulting in a lower energy state and a more stable molecule.
Example: Carbon Dioxide (CO₂)
Carbon dioxide (CO₂) provides a clear example.
- Carbon's Need: A carbon atom has 4 valence electrons and needs 4 more to complete its octet.
- Oxygen's Need: Each oxygen atom has 6 valence electrons and needs 2 more to complete its octet.
- The Solution: Double Bonds: The carbon atom shares two electrons with each oxygen atom, forming two double covalent bonds. This arrangement allows the carbon atom to achieve an octet (4 original + 4 shared) and each oxygen atom to achieve an octet (6 original + 2 shared).
O = C = OIn this structure, each line represents a shared pair of electrons, indicating a covalent bond. The double lines indicate double bonds.
