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The Alchemists

500 BCE

All metals were formed from 2 principles. Mercury and Sulfur

Democritus

460 BCE

Atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through empty space until stopped.

Plato

440 BCE

Solid forms of matter are composed of indivisible elements shaped like triangles

Antoine Lavoisier

1789

Defined that matter was composed of atoms that were not created or destroyed during chemical reactions.

Amedeo Avogadro

1811

Equal volumes of gases at the same temperature and pressure contain the same number of molecules regardless of their chemical nature and physical properties.

Dmitri Mendeleev

1869

Elements arranged according to the value of their atomic weights present a clear periodicity of properties

JJ Thompson

1897

All atoms contain tiny negatively charged subatomic particles or electrons.

Pierre and Marie Curie

1898

She suggested that the powerful rays, or energy, the polonium and radium gave off were actually particles from tiny atoms that were disintegrating inside the elements.

Albert Einstein

1905

Any liquid is made up of molecules

robert millikan

1910

Millikan's work demonstrated that electrons did have a discrete, quantifiable charge

ernest rutherford

1911

Described the atom as having a tiny, dense, and positively charged core called the nucleus

neils bohr

1913

Some physical quantities only take discrete values

henry G. J. Mosely

1914

Atomic numbers are the fundamental feature that describes an element.

james chadwich

1932

Discovery of the neutron.