Covalent Bond Formation and Hybridization

Overview

This lecture explains how covalent bonds form at the atomic level, emphasizing electron sharing, atomic orbital overlap, and the concept of hybridization, especially for hydrogen and carbon atoms.

Covalent Bond Formation

• Two hydrogen atoms react to form a covalent bond by sharing electrons.
• Covalent bonds involve the sharing of electron density between two atoms.
• Covalent bonding is represented as a shared pair of electrons or a single bond.

Atomic Orbitals and Wave Interference

• Electrons in atoms are found in orbitals, regions with a high probability of electron presence.
• Orbitals can be considered as waves; if two atomic orbitals overlap in phase, constructive interference forms a bond.
• Out-of-phase overlap (destructive interference) creates a node—an area with almost zero electron density.
• Head-to-head overlap of orbitals produces a sigma (σ) bond; all single bonds are sigma bonds.

Carbon Hybridization and Methane Formation

• Carbon's ground state electron configuration: 1s² 2s² 2p², with four valence electrons.
• Hybridization: Mixing 2s and three 2p orbitals produces four sp³ hybrid orbitals (degenerate, equal energy).
• Each sp³ orbital is 25% s character and 75% p character.
• In methane (CH₄), carbon uses four sp³ orbitals to form four sigma bonds with hydrogen atoms.
• The C-H bond in methane is described as an overlap of an sp³ hybrid orbital from carbon and an s orbital from hydrogen.

Examples: Ethane and Quick Hybridization Rules

• Ethane (C₂H₆) contains seven sigma bonds, with each carbon atom sp³ hybridized.
• For hydrogen, the orbital is always s since it forms only one bond.
• Rule: Carbon with four attached atoms = sp³; three atoms = sp²; two atoms = sp.

Key Terms & Definitions

• Covalent Bond — a bond formed by the sharing of electrons between two atoms.
• Atomic Orbital — a region around an atom's nucleus with a high probability of finding an electron.
• Sigma (σ) Bond — a bond formed by head-to-head orbital overlap; all single bonds are sigma bonds.
• Hybridization — mixing atomic orbitals to form new, degenerate hybrid orbitals.
• sp³ Orbital — a hybrid orbital formed from one s and three p orbitals (25% s, 75% p character).
• Node — a region of zero electron density due to destructive interference between orbitals.
• Degenerate Orbitals — orbitals with the same energy.

Action Items / Next Steps

• Practice identifying the hybridization of carbon atoms in various molecules.
• Review electron configurations and orbital diagrams for hydrogen and carbon.