-
450 BCE
Four Elements
The Greek Philosopher Empedocles, stated a theory that was not later established til the 17th century. All matter is made up, in differing proportions, of four elemental substances. -
420 BCE
The Atom
Democritus states that all matter is composed of small substances that cling together in differing combinations to create the objects around us. -
330 BCE
Transmutation
Aristotle supported Empedocles' theory. Later, transmutation of water into Earth was a basic principle to his theory. -
Henry Cavendish
He was a natural philosopher, the greatest experimental and theoretical chemist and physicist of his time. He studies included the composition of air, the properties of different gases, the synthesis of water, the law governing electrical attraction and repulsion, a mechanical theory of heat, and calculations of the
density of Earth. -
"Discover Oxygen"
Joseph Priestly was a teacher, preacher, and scientist who studied air and invented "Carbonated Water". In 1774 he conducted a famous experiment to generate O2 from heating reddish
mercury oxide, and found the new air was many times
as good as common air. -
Modern Chemistry
Antoine- Laurent Lavoiser classified matter into three states; Solids, Liquids, and Gas. He studied air and metals, found oxygen, hydrogen, and sulfur. Defined element
as simple substance that could not be
analyzed by chemical means; the law of mass
conservation and metric system -
Dmitri Ivanovich Mendeleev
A Russian Chemist and Inventor, created the Periodic Law and created a farsighted version of the Periodic Table of Elements. -
Julius Lothar Meyer
Also independently published a periodic table and split a pre-
Noble Prize, Davy Medal in 1882. -
Lord Rayleigh
In the 1880s he made the discovery that the density of nitrogen obtained from the atmosphere is greater by a small and definite amount that the density of nitrogen obtained from one of its chemical compounds. He later worked with Sir William Ramsay which proved a new element, argon. -
The Discovery of Radon
Radon was first identified by a German chemist, Fredrich E. Dorn; it was later established to be a member of the noble gases. -
Noble Gases
Sir William Ramsay was a British physical chemist who discovered the four following gases; neon, argon, krypton, and xenon. These gases along with helium and radon formed an entire family of new elements know as the noble gases. In 1904 he was awarded a noble prize.
