| Year | Scientist(s) | Development |
|---|---|---|
| 1916 | G.N. Lewis | Lewis dot structures; octet rule; covalent bond as shared electron pair |
| 1916 | W. Kossel | Ionic bonding theory; electrovalence; Born's work on ionic crystals |
| 1918 | I. Langmuir | Expanded Lewis theory; coined terms "covalent bond" and "valence" |
| 1923 | G.N. Lewis, N.V. Sidgwick | Lewis acid-base theory; coordinate (dative) bonds |
| 1927 | W. Heitler, F. London | Quantum mechanical VBT for ; wave function overlap model |
| 1928 | R.S. Mulliken | LCAO approach; first MOT formulation |
| 1931 | L. Pauling | Hybridization concept; resonance theory; electronegativity scale (1932) |
| 1939 | R.S. Mulliken | Formal MOT theory; bond order concept |
| 1957 | R.J. Gillespie, R.S. Nyholm | Modern VSEPR theory formulation |
| 1939–1940 | M. Born, J.E. Mayer | Born-Mayer equation for lattice energy |
| 1920s | K. Fajans | Fajan's rules for polarisation and covalent character in ionic bonds |
| 1954 | L. Pauling | Nobel Prize in Chemistry for VBT and chemical bond theory |
Key Insight
VSEPR (1957) was a later refinement that made geometry prediction accessible without full quantum calculations. MOT correctly handles paramagnetism ( discovery was a key experimental test in ~1930s). Pauling's electronegativity scale remains the most widely used today.