Democritus 440
All matter is made up of atoms
Atomos /Atoms- small, invisible, indestructible and physically indivisible particles which are infinite in number

Issac Newton 1704
Defined the laws of gravity and motion
Newton's law of gravity-all objects attract everything other object in the universe with gravitational forces.
Atoms are solid, hard, impenetrable, moveable particles
Newton’s laws of gravity and motion -atoms are held together by opposing forces.

John Dalton 1803
Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass.

Michael Faraday 1832
Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, developed laws of electrolysis.

J. Plucker 1859 built one of the first cathode-ray tubes

Dmitri Mendeleev 1869
Discovered and arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law.

James Clerk Maxwell 1873 proposed the theory of electromagnetism and made the connection between light and electromagnetic waves

E Goldstein 1886 discovered canal rays, which have a positive charge equal to an electron

George Johnstone Stoney 1894
Determined that electricity was made of negative particles. In 1891, he named these negative particles “electrons”

Wilhelm Roentgen- 1895 discovered x-rays

Henri Becquerel 1896 discovered radiation by studying the effects of x-rays on photographic film.

J.J. Thompson 1897
Reconfirmed Stoney’s theory. Thompson discovered that atoms contain negative particles known as electrons inside a cloud of positive charge.

Ernest Rutherford 1898
Studied radiations emitted from uranium and thorium and named them alpha and beta.

Frederick Soddy 1900 came up with the term "isotope" to explain the unintentional breakdown of radioactive elements

Hantaro Nagaoka 1903 proposed an atomic model called the Saturnian Model to