Atomic Theory Timeline

By Jcarter-mckinley3520
  • 400 BCE

    Democritus

    400 B.C. the Greek philosopher Democritus suggested that all matter was formed of different types of tiny discrete particles and that the properties of these particles also determined the properties of matter. His mentor, Leucippus, originally came up with the atomic theory, but it was then adopted by Democritus.
  • 384 BCE

    Aristotle

    Ancient Greek philosopher Aristotle was born circa 384 B.C. in Stagira, Greece. When he turned 17, he enrolled in Plato's Academy. In 338, he began tutoring Alexander the Great. Aristotle did not believe in the atomic theory and he taught so otherwise. He thought that all materials on Earth were not made of atoms, but of the four elements, Earth, Fire, Water, and Air. He believed all substances were made of small amounts of these four elements of matter.

  • Antoine Lavoisier

    French chemist Antoine Lavoisier between 1772 and 1794. Lavoisier found that mass is conserved in a chemical reaction. ... But the number of hydrogen and oxygen atoms before and after the reaction is the same.

  • Joseph Louis Proust

    He was best known for his discovery of the law of constant composition in 1794, stating that chemical compounds always combine in constant proportions. This law states that a compound is composed of exact proportions of elements by mass regardless of how the compound was created.

  • John Dalton

    1803 he revealed the concept of Dalton's Law of Partial Pressures. All matter is made of atoms. Atoms are indivisible and indestructible.All atoms of a given element are identical in mass and properties.

  • Michael Faraday

    1831, Faraday discovered electromagnetic induction, the principle behind the electric transformer and generator. contributed to the fields of electromagnetism and electrochemistry.

  • Henri Becquerel

    1896, he discovered radioactivity, which was to be the focus of his work thereafter. Becquerel won the Nobel Prize for Physics in 1903, sharing the prize with Marie and Pierre Curie. contribution to our understanding of atomic theory when he discovered the existence of radioactivity.

  • J.J. Thomson

    1897 designed to study the nature of electric discharge in a high-vacuum cathode-ray tube, J.J. Thomson discovered the electron by experimenting with a Crookes, or cathode ray, tube. He demonstrated that cathode rays were negatively charged. In addition, he also studied positively charged particles in neon gas.

  • Marie & Pierre Curie

    1898 of the elements radium and polonium. Curie began the systematic study of other elements to see if there were others that also emitted this strange energy. Within days she discovered that thorium also emitted radiation, and further, that the amount of radiation depended upon the amount of element present in the compound.

  • Ernest Rutherford

    Rutherford discovered the nucleus of the atom in 1911. Rutherford overturned Thomson's model in 1911 with his well-known gold foil experiment in which he demonstrated that the atom has a tiny, heavy,nucleus.Rutherford designed an experiment to use the alpha particles emitted by a radioactive element as probes to the unseen world of atomic structure.

  • Neils Bohr

    In 1913, on the basis of Rutherford's theories, Bohr developed and published his model of atomic structure, known as the Bohr model, which depicts the atom as a small, positively-charged nucleus surrounded by negatively-charged electrons that travel in circular orbits around the nucleus, similar in structure to the Solar System, but with electromagnetic forces providing attraction, rather than gravity.

  • Max Planck

    German theoretical physicist who originated quantum theory, which won him the Nobel Prize for Physics in 1918. theory of energy for which he was awarded the Nobel Prize in 1918. His work contributed significantly to the understanding of atomic and subatomic processes.

  • Albert Einstein

    In 1922, he was awarded the 1921 Nobel Prize in Physics "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect". which laid the basis for the release of atomic energy. In 1905 Albert Einstein formulates Special Theory of Relativity. Einstein calculates how the movement of molecules in a liquid can cause the Brownian motion.

  • Robert Millikan

    American experimental physicist honored with the Nobel Prize for Physics in 1923 for the measurement of the elementary electronic charge and for his work on the photoelectric effect. His oil drop experiment helped to quantify the charge of an electron, which contributed greatly to our understanding of the structure of the atom and atomic theory.

  • James Chadwick

    1935 Nobel Prize in Physics for his discovery of the neutron in 1932. James Chadwick played a vital role in the atomic theory, as he discovered the Neutron in atoms. Neutrons are located in the center of an atom, in the nucleus along with the protons. They have neither a positive nor negative charge, but contribute the the atomic weight with the same effect as a proton.