Two dots between two letters
The starting claim is disarmingly simple: that a chemical bond between two atoms can be understood as a shared pair of electrons. Gilbert Lewis proposed exactly this in 1916, representing valence electrons as dots around an atomic symbol and a shared pair sitting between two atoms as the bond itself. This gave chemists a notation, now familiar from any introductory chemistry class, that could represent single, double and triple bonds simply by drawing one, two or three shared electron pairs between a given pair of atoms, without requiring any deeper physical theory of why sharing electrons should hold atoms together at all.
A name, then a proof
The idea acquired both a name and, eventually, a genuine physical foundation. Irving Langmuir introduced the term covalence in a 1919 paper, defining it as the number of electron pairs a given atom shares with its neighbours, which gave Lewis’s notation a settled vocabulary. The deeper justification came later still: Walter Heitler and Fritz London provided the first successful quantum-mechanical explanation of a covalent bond in 1927, applying the new tools of quantum theory specifically to the hydrogen molecule and showing that electron sharing between two atoms could genuinely lower the system’s energy in the way Lewis’s picture had simply assumed.
Pauling turns a sketch into a framework
Linus Pauling built the fullest version of this framework from that quantum-mechanical starting point. He introduced the concept of electronegativity in 1932, along with a numerical scale that let chemists predict how a bond’s character would shift toward ionic or covalent depending on which two elements were involved. He also showed that an atom’s orbitals could be mathematically combined into hybrid forms — four equivalent orbitals for carbon in methane, a different combination for the double bonds in ethylene — and developed resonance theory, arguing that a molecule like benzene was best described not as flipping rapidly between two structures but as an intermediate blend of both at once.
A textbook cited sixteen thousand times
The scale of this framework’s acceptance is measurable rather than just asserted. Pauling’s 1939 book, The Nature of the Chemical Bond, gathered electronegativity, hybridisation and resonance into a single coherent account of bonding, and in the thirty years following its first edition it was cited more than sixteen thousand times, a mark of how thoroughly it became the standard reference for the subject. The bonding work earned Pauling an unshared 1954 Nobel Prize in Chemistry, and combined with his unshared 1962 Nobel Peace Prize for nuclear disarmament advocacy, made him the only person to hold two unshared Nobel Prizes.
The same certainty applied somewhere it didn’t belong
That record of getting fundamental chemistry right did not transfer automatically to Pauling’s later medical claims. Beginning in 1966 he took up megadose vitamin C therapy, publishing Vitamin C and the Common Cold in 1970 and, working with surgeon Ewan Cameron from 1971, claiming that high-dose vitamin C could increase survival in terminal cancer patients by as much as fourfold compared with untreated patients. A re-evaluation of these claims in 1982 found the patient groups being compared were not actually alike, undermining the basis for the reported effect, and the therapy has not gained meaningful acceptance in mainstream medicine since.
One legacy earned twice, in different currencies
What makes this worth sitting with is the contrast rather than either half alone. The bonding work survived because it was built on, and tested against, an increasingly rigorous quantum-mechanical foundation that other researchers could check and extend, which is exactly the kind of scrutiny the vitamin C claims did not receive before Pauling advanced them with comparable confidence. A towering reputation in one field earned through demonstrated, checkable results is not evidence in a different field, and this is as clean an illustration of that distinction as the history of science offers — one Nobel Prize built on results that held, the later medical claims built on a comparison that, checked properly, did not.