History of Chemistry

Empedopcles

four elements

Democritus

all matter comes from indestructible atoms; four elements are made from atoms

Aristotle

four elements with four properties; combined to form all matter

Roger Bacon

experiments important to development of knowledge

Robert Boyle

atoms of different shapes and sizes; Boyle’s law

Joseph Proust

law of definite proportions

John Dalton

atomic theory; elements have constant mass and compounds are made of elements

Jons Jacob Berzelius

introduced modern symbols to the periodic table; determined atomic weight of many elements

Dmitri Mendeleev

created first modern periodic table using periodic law

J.J. Thomson

discovery of proton; plum pudding model of the atom

Nagaoka

“saturnian” model; electrons orbit positive nucleus

Robert Millikan

Millikan oil drop experiment; determined the mass and charge of the electron

Ernest Rutherford

Postulated a positively charged nucleus based off of gold foil experiment

Henry Moseley 

atoms are ordered by number of protons

Niels Bohr

Bohr’s model: stationary states of electrons that orbit in shells; planetary model

Erwin Schrodinger

electron cloud model; electrons behave as waves

Current model

electron cloud-probability distribution