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440
Democritus
Democritus, commonly known as the 'Father of Modern Science', believed that if you kept cutting an object, you would eventually end wih an uncuttable, homogeneous piece, called an 'atom'. -
Period: 460 to
Atomic Theory Through the Ages
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John Dalton
John Dalton's theory included:
-all substances are made of atoms (undestructable particles)
-atoms of the same element are exactly alike
-atoms join with other atoms to make new substances
His model was named 'Billiard Balls'. -
George Johnstone Stoney
George Johnstone Stoney is known for proposing the term 'electron' which is the "fundamental unit quantity of electricity". -
Joseph John Thomson
J.J. Thomson believed that atoms could be divided into smaller parts and that there were positive and negative charges in atoms. In his, 'Plum Pudding' model, he discovered our modern day electrons. -
Max Planck
Max Planck is most famous for being the inventor of the Quantum Theory which describes energy being emitted in quanta. He is also proposed the quantum of action or 'Planck's constant'. -
Erwin Schrodinger
Erwin Schrodinger proposed that electrons moved in shells around the nucleus within Electron Clouds (based off of his wave equation). -
Ernest Rutherford
Ernest Rutherford, who is most commonly known for first splitiing an atom, proposed that an extremely small and very dense, positively charged nucleus was in the middle of an atom. Also, he believed there were positive charges outside of the atom. Rutheford called his model the 'planetary' model. (He is also credited for the Geiger–Marsden experiment) -
Henry Moseley
Henry Moseley discovered the number of protons in a nucleus determines the atom's identity thus justifying the atomic number from his development of X-ray spectra. Our modern day periodic table is based off of his findings. -
Niel Henrik David Bohr
Niel Bohr believed that electrons are located in levels at certain distances fromthe nucleus.He also proposed that electrons orbit the nucleus in a stationary orbit which is shown in the Bohr model. -
James Chadwick
James Chadwick proved the existence of uncharged particles in atoms; neutrons. Neutrons stabilize the atoms nucleus, help reduce the repulsion between protons, and play a large role in nuclear fission. His model showed protons and neutrons in the nucleus with electrons outside of it.
