From Oxygen to the Chemical Bond: Eleven Chemists in Order of Their Key Work

On 1 August 1774 Priestley heated red mercuric oxide with a burning lens and collected a gas in which a candle burned unusually brightly and mice survived far longer than in ordinary air. He read the result through phlogiston theory and called it dephlogisticated air, and he never accepted Lavoisier's reinterpretation of it as oxygen.

Scheele made the same gas by heating mercuric oxide as early as 1771 to 1772 and called it fire air, but his manuscript sent to the printer in 1775 did not appear until 1777, after Priestley had published. His 1774 letter to Lavoisier went missing for more than two centuries and became public only in 1992, which is why priority for oxygen is usually given to Priestley.

In his 1808 book A New System of Chemical Philosophy, Dalton proposed that each element is made of identical, indivisible atoms of a characteristic weight and that compounds form when atoms combine in small whole-number ratios. The idea explained the law of multiple proportions and let chemists calculate relative atomic weights for the first time.

From 1813 Berzelius introduced the notation chemists still use, giving each element one or two letters from its Latin name and marking atom counts with numeral subscripts in place of the pictorial and alchemical symbols earlier chemists had used. He also determined atomic weights for a large share of the known elements and was among the first prominent chemists to accept Dalton's atomic theory.

Kekule proposed that carbon atoms are tetravalent and bond in chains, and in 1865 that benzene is a ring of six carbon atoms. The ring structure is not in question. The famous story of a dream of a snake seizing its own tail was told only in 1890, twenty-five years later, and historians treat it with caution because no contemporary record supports it.

In 1869 Mendeleev arranged the known elements by atomic weight into columns of similar behavior, and where the pattern needed an unknown element he left a gap and predicted its properties. His forecasts for eka-aluminium, eka-boron and eka-silicon were matched by the discoveries of gallium in 1875, scandium in 1879 and germanium in 1886, which is why the table counts as a theoretical achievement and not only a filing system.

With his wife Marie, Pierre Curie isolated the new elements polonium and radium from pitchblende ore in 1898, using fractional crystallization of tons of ore to obtain barely visible quantities of each. He shared the 1903 Nobel Prize in Physics with Marie Curie and Henri Becquerel. He is the one physicist on this path, included because the Curies added two elements to the table.

On 2 July 1909 Haber demonstrated a laboratory process for making ammonia directly from nitrogen and hydrogen under high pressure over a metal catalyst. He received the 1918 Nobel Prize in Chemistry for it, amid protest over his separate wartime role directing the first large-scale chlorine gas attack, at the Second Battle of Ypres on 22 April 1915.

Between 1909 and 1913 Bosch led the effort at BASF to scale Haber's laboratory reaction into an industrial process, solving problems of high-pressure vessel design, catalyst durability and hydrogen supply. He shared the 1931 Nobel Prize in Chemistry with Friedrich Bergius for high-pressure chemical methods.

In his 1916 paper The Atom and the Molecule, Lewis proposed that a covalent bond is a pair of electrons shared between two atoms, and introduced the dot diagrams that now carry his name. In 1923 he generalized acids and bases as acceptors and donors of an electron pair. Nominated for the Nobel Prize repeatedly across three decades, he never won it.

Pauling applied the new quantum mechanics to bonding in the 1930s, developing orbital hybridization, resonance and an electronegativity scale. His 1939 book The Nature of the Chemical Bond extended Lewis's shared electron pair into a full quantum-mechanical account, and he won the 1954 Nobel Prize in Chemistry for it. He also won the 1962 Nobel Peace Prize.