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546 BCE
Thales
sometimes referred to as the “father of science” although this epithet is usually used in reference to Democritus, another prominent ancient Greek philosopher who formulated the atomic theory that states that all matter is composed of particles called atoms. -
400 BCE
Democritus
Democritus was the first to identify the possibility of an atom, which would be the smallest piece of matter. The fundamental idea in Democritus's theory is that nature behaves like a machine, it is nothing more than a highly complex mechanism. Aristotle did not agree with democritus' theory. -
380 BCE
Aristotle
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. -
Isaac Newton
Newton formulated a theory of light, the three laws of motion and suggested a mechanical universe with small, solid masses in motion.
Contribution to our understanding of the atom: Newton suggested that atoms are held together with attractions, otherwise known as forces. He also stated that "matter is formed of solid, massy impenetrable particles”. -
Michael Faraday
In an article he wrote for the Manchester Literary and Philosophical Society in 1803, Dalton created the first chart of atomic weights. Seeking to expand on his theory, he readdressed the subject of atomic weight in his book A New System of Chemical Philosophy, published 1808. -
John Dalton
He proposed an atomic theory.
Contribution to our understanding of the atom: Dalton stated (1) all matter was composed of small indivisible particles termed atoms, (2) atoms of a given element possess unique characteristics and weight, and (3) three types of atoms exist: simple (elements), compound (simple molecules), and complex (complex molecules). -
Sir William crookes
Sir William Crookes, British chemist and physicist noted for his discovery of the element thallium and for his cathode-ray studies, fundamental in the development of atomic physics -
Max planck
German theoretical physicist who originated quantum theory, which won him the Nobel Prize for Physics in 1918. -
Dmitri mendeleev
Transcript of Dmitri Mendeleev's atomic theory. Dmitri Mendeleev's theory was arranging the sixty three elements based on atomic mass into a periodic table. -
G.J. Stoney
George Johnstone Stoney FRS (15 February 1826 – 5 July 1911) was an Anglo-Irish physicist. He is most famous for introducing the term electron as the fundamental unit quantity of electricity. -
E. Goldstein
Eugen Goldstein was a German physicist. He was an early investigator of discharge tubes, the discoverer of anode rays, and is sometimes credited with the discovery of the proton. -
J.J. Thomson
Sir Joseph John Thomson OM PRS was an English physicist and Nobel laureate in physics, credited with the discovery and identification of the electron; and with the discovery of the first subatomic particle. -
Marie sklodowska curie
For their joint research into radioactivity, Marie and Pierre Curie were awarded the 1903 Nobel Prize in Physics. As a team, the Curies would go on to even greater scientific discoveries. In 1898, they announced the discovery of two new elements, radium and polonium. -
Hantaro nagaoka
In 1904, Nagaoka proposed an alternative planetary model of the atom in which a positively charged center is surrounded by a number of revolving electrons, in the manner of Saturn and its rings. Nagaoka's model made two predictions: a very massive atomic center (in analogy to a very massive planet). -
Richard Abegg
Richard Abegg. Richard Wilhelm Heinrich Abegg was a German chemist and pioneer of valence theory. He proposed that the difference of the maximum positive and negative valence of an element tends to be eight. -
Rutherford
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. -
Niels Bohr
In 1913, Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted. -
H.G.J. Mosely
Henry Gwyn Jeffreys Moseley was an English physicist, whose contribution to the science of physics was the justification from physical laws of the previous empirical and chemical concept of the atomic number. -
Frederick soddy
Frederick Soddy was an English radiochemist who explained, with Ernest Rutherford, that radioactivity is due to the transmutation of elements, now known to involve nuclear reactions. He also proved the existence of isotopes of certain radioactive elements. -
Francis William
British physicist who won the Nobel Prize for Chemistry in 1922 for his discovery of a large number of isotopes (atoms of the same element that differ in mass), using a mass spectrometer. -
Louis de Brofile
French physicist best known for his research on quantum theory and for predicting the wave nature of electrons.
