Molecular Structure & Chemical Bonding

VSEPR theory and molecular geometry in 3D

Chemical bonding determines molecular geometry, polarity, and reactivity. Covalent bonds form when atoms share electrons; the electronegativity difference determines polarity (nonpolar < 0.5, polar 0.5-1.7, ionic > 1.7). VSEPR theory predicts 3D geometry: electron pairs (bonding + lone) arrange to minimize repulsion. Lone pairs repel more strongly than bonding pairs, compressing bond angles. Linear (180°): CO₂, BeCl₂. Trigonal planar (120°): BF₃. Tetrahedral (109.5°): CH₄. Bent (104.5°): H₂O (2 lone pairs). Trigonal pyramidal (107°): NH₃ (1 lone pair). Octahedral (90°): SF₆. Net molecular dipole moment = vector sum of all bond dipoles.