Chemistry Timeline

Discoveries

Benjamin Franklin's lightning Rod experiment promotes more experiments with electricity.

1752

William Crookes discovers cathode rays and their properties.

1856

Wilhelm Roentgen discovers X-rays

1895

J.J. Thompson discovers that electrons are negatively charged,.

1897

Antoine Becquerel proves radioactivity

1903

Pierre/Marie Curie discover multiple radioactive elements and properties

1903 - 1911

Rutherford discovers the nucleus, and the protons contained within.

1910

Millikan determine electrons charge and its constancy

1910

Theories

Democritus proposes that everything is made of different, indivisible particles.

400 B.C

Anaxagoras Proposes there is no largest or smallest unit of mass, everything will grow and divide infinitely.

400 B.C.

Dalton creates the first modern atomic model

1803

Dalton proposed that all matter is made up of indivisible and indestructible atoms. He proposed that each element had unique atoms, with unique properties. This led him to conclude that chemical reactions were simply the rearrangement of atoms.

Niels Bohr proposes that electrons orbit the nucleus in quarantined levels

1913

James Chadwick discovers the neutron within the nucleus.

1932

Laws

Law of Conservation of Mass

Approx. 1789

Law of Definite Composition

1796

Law of Multiple Proportions

1804