Swedish chemist Alfred Nobel patents dynamite, making the volatile explosive nitroglycerine safer by combining it with kieselguhr

Dmitry Mendeleyev reads to the Russian Chemical Society in St Petersburg his formulation of the periodic table

Scottish chemist William Ramsay isolates the element helium

British chemists William Ramsay and Morris Travers isolate the element c

British chemists William Ramsay and Morris Travers isolate the element neon

British chemists William Ramsay and Morris Travers isolate the element xenon

Marie Curie and her husband Pierre isolate a new element which they name polonium in honour of her native Poland

Marie and Pierre Curie isolate the element radium, working without any protection because unaware of the danger of radioactivity

Frederick Soddy observes his first examples of chemically identical elements with differing atomic weights, to which he later gives the name isotopes

Albert Einstein formulates the law of photochemical equivalence, a fundamental principle of chemical reactions induced by light

Frederick Soddy uses the term 'isotope' (Greek for 'same place') to describe observed anomalies in the periodic table

Linus Pauling, a graduate student at the California Institute of Technology, begins theoretical work on the nature of the chemical bond

US chemist Linus Pauling publishes his collected discoveries on The nature of the chemical bond

British chemist Dorothy Hodgkin describes the molecular structure of penicillin

The technique of radiocarbon dating is developed by US chemist Willard Libby

Syntex, a small chemical company in Mexico City, develops the first oral contraceptive

The drug Thalidomide, synthesized in West Germany, is shown to have been the cause of severe defects in about 12,000 children born in 46 countries