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Antoine Lavoisier
He found the law of conservation of mass: Matter cannot be created or destroyed. -
Joseph Proust
He created the principle known as the law of definite proportions: specific substances always contain elements in the same ratio by mass. -
John Dalton
Found that all matter is composed of atoms, all matter of the same element have the identical atoms, atoms of different elements are not alike, and atoms unite in simple ratios to form compounds. -
John Dalton No. 2
He discovered the Law of Multiple Proportions: The ratio of masses of one element that combine with a constant mass of another element that can be expressed in small whole numbers. -
J. L. Gay-Lussac
He found that under constant conditions the volumes of reacting gases and gaseous products are in the ratio of small whole numbers. -
Amadeo Avagadro
He stated that equal volumes of gases, under the same conditions, have the same number of molecules. -
Dimitri Mendeleev
He proposed the periodic law and developed the first periodic table. -
Henri Becquerel
He found that matter containing uranium exposes sealed photographic film. -
J.J. Thomson
researched cathode rays and was able to determine the ration of an electron’s charge to its mass.. Found that cathode rays consist of electrons. -
Marie and Pierre Curie
Found that rays are given off by the elements uranium and radium. -
Robert Millikan
Obtained the first acurate measurement of an electrons charge. -
Henry Mosely
Found out about the atomic number by studying x-rays with anodes of different materials. Finding that the number of protons determines the identity of the element and the number of neutrons determines the particular isotope of the element. -
Lord Rutherford
he predicted the existence of the neutron. He also proposed the nuclear atom as the result of the gold-foil experiment -
Walter Bothe
Obtained the first evidence of the neutron. -
James Chadwick
He discovered the neutron.
