History ofthe Atom

Democritus

460

460BC - Democritus - stated that all matter is made up of atoms. He also stated that atoms are eternal and invisible and so small that they can’t be divided, and they entirely fill up the space they’re in. Later Aristotle dismissed the atomic idea as worthless. People considered Aristotle's opinions very important and if Aristotle thought the atomic idea had no merit, then most other people thought the same also.

Lavoisier

Sep 25, 1777

1777 - Lavoisier - provided the formula for the conservation of matter in chemical reactions, and also distinguished between an element and a compound

Couloumb

Sep 25, 1780

1780 - Couloumb - formulated the Coulomb's law, which states that that the force between two electrical charges is proportional to the product of the charges and inversely proportional to the square of the distance between them, one of the main forces involved in atomic reactions.

John Dalton

Sep 25, 1803

1803 - John Dalton - formed the atomic theory, which states that all matter is composed of tiny, indestructible particles called atoms that are all alike and have the same atomic weight.

Henri Becquerel

Sep 25, 1896

1896 - Henri Becquerel - discovered radioactivity when he investigated uranium and other radioactive substances.

Marie and Pierre Curie

Sep 25, 1898

1898 - Marie and Pierre Curie - discovered radium and polonium when they started to investigate radioactive substances

J.J. Thomson

Sep 25, 1898

1898 - J.J. Thomson - discovered the electron and developed the plum-pudding model of the atom.

Max Planck

Sep 25, 1900

1900 - Max Planck - originated the quantum theory

Albert Einstein

Sep 25, 1905

1905 - Albert Eintein - postulated that light was made up of different particles that, in addition to wavelike behavior, demonstrate certain properties unique to particles. He also brought forth the theory of relativity.

Robert Millikan

Sep 25, 1908

1908 - Robert Millikan - found out the electric charge of the electron

Ernest Rutherford

Sep 25, 1909

1909 - Ernest Rutherford - used the results of his gold-foil experiment to state that all the mass of an atom were in a small positively-charged ball at the center of the atom.

Neils Bohr

Sep 25, 1913

1913 - Neils Bohr - stated that the electrons moved around the nucleus in successively large orbits. He also presented the Bohr atomic model which stated that atoms absorb or emit radiation only when the electrons abruptly jump between allowed, or stationary, states.

Henry Mosely

Sep 25, 1913

1913 - Henry Mosely - discovers a relationship between the atomic number(he also discovered the meaning) and nuclear charge and he also validated the Rutherford/Van den Broek/Bohr nuclear model of the atom.

Louis de Broglie

Sep 25, 1921

1921 - Louis de Broglie - introduces the wave/particle duality of matter

Werner Heisenburg

Sep 25, 1923

1923 - Werner Heisenberg - elucidated the Uncertainty Principle. He worked out that particles had a lot more energy over short distances than expected. He realized that a particle can borrow energy as long as it is paid back in a short time. The relationship he came up with was the position and energy of a particle can only be known to a certain amount. (the certainty in position and the certainty in momentum is more or less equal to plank's constant).

Geiger

Sep 25, 1925

1925 - Geiger - introduced the first detector of alpha particles and other radiations.

Erwin Shroedinger

Sep 25, 1926

1926 - Erwin Shroedinger - introduced the Shroedinger Equation, a wave equation that describes the form of the probability waves that govern the motion of small particles and how these waves are altered by external influences.

Chadwick

Sep 25, 1931

1931 - Chadwick - discovered the neutrally-charged neutron.

Otto Hahn and Lise Meitner

Sep 25, 1938

1938 - Otto Hahn - Lise Meitner - discovered nuclear fission, in which the nucleus of an atom breaks up into two separate nuclei, while experimenting with uranium. Lise Meitner also helped him to discover uranium fission.

Glenn T. Seaborg

Sep 25, 1951

1951 - Glenn T. Seaborg - isolated and identified elements heavier than uranium, and in the process, added elements number 94 - 102, and 106 (aka Plutonium, Americium, Curium, Berkelium, Californium, Einsteinium, Fermium, Mendelevium, Nobelium, and Seaborgium).

Murry Gell-Mann and George Zweig

Sep 25, 1964

1964 - Murry Gell-Mann - George Zweig - brought forth the idea of "quarks", little bits of matter which when used kind of like building blocks, serve to explain some complex chemical substances.

Aristotle

Mar 2, 2022

338BC - Aristotle - provided the method of gathering scientific facts, which proved as the basis for all scientific work.