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400 BCE
Democritus
He 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. -
John Dalton
He found that all matter was composed of atoms, indivisible and indestructible building blocks. -
Dmitri Mendelev
He is known for his work on the Periodic Law and creation of the first Periodic table. -
Eugen Goldstein
He was one of the first to observe the proton. -
J.J. Thomson
He discovered the electron by experimenting with a Crookes, or cathode ray, tube. He demonstrated that cathode rays were negatively charged. -
Max Planck
He is best known as the originator of the quantum theory of energy for which he was awarded the Nobel Prize in 1918. -
Robert Millikan
He helped us for allowing us to find the calculation of the mass of the electron and the positively charged atoms. -
Ernest Rutherford
He was the first to discover that atoms have a small charged nucleus surrounded by largely empty space, and are circled by tiny electrons, which became known as the Rutherford model. -
Niels Bohr
He developed a theory for the hydrogen atom. 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. -
Werner Heisenberg
He discovered a way to formulate quantum mechanics in terms of matrices. -
Erwin Schrodinger
He took the Bohr model further. He described the likelihood of finding an electron in a certain position. -
James Chadwick
He found that 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.
