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Aristotle
Aristotle didn't like the idea of the atom. He claimed that there was no smallest part of matter. He said that different substances were made up of only fire, air, earth, and water. -
Democritus
Democritus developed the idea of an atom. He thought that if you break a peice of matter in half, how many times could it be broken until you couldn't brake it any more. -
John Dalton
Dalton said that all elements are composed of atoms, all atoms of the same element havethe same mass, but atoms of different elements have different masses, compounds have atoms of more than 1 element, atoms always combine the same way. Dalton concluded hois information by measuring the masses of elements that combine after compounds form. -
G.J Stoney
Stoney proposed that electricity was made of negative particles he called electrons. -
J.J Thompson
J.J Thompson discovered the electron. Thompson discovered this by creating a positive and negative charge by using electricaly charged plates and magnets as evidence of bodies much smaller than atoms. -
Hantaro Nagaoka
Stated that atoms have a central nuecleus, and electrons orbit like rings that orbit the planet saturn.The electrons orbit around the nucleus gives itself a positively electric charge. -
Ernest Marsden
Worked under the supervision of Ernest Rutherford. Did the gold foil expieriment with Ernest Rutherford, they shot alpha particles off thing sheet of gold and observed large angles. Assuming that atoms have a small dense positively charged nucleus. -
Ernest Rutherford
Says that an atom has a dense posativley charged nucleus. The electrons move freely around the nucleus. He shot a positively charged helium particle into a very thing layer of gold. -
Neils Bohr
Stated electrons move in spherical orbits at fixed distances around the nucleus. He is also the one who discovered that Ernest Rutherford's model had a few problems. -
Francis William Aston
Aston dicovered that isotopes exist through a spectrohraph. -
Louis de Broglie
Said that particles that move like electrons do have some properties of waves. A few years after Broglie stated this he collected information for his idea. -
Erwin Schrodinger
Developed math equations to describe the motionof electrons in all atoms. This work later lead to the dicovery of the electron cloud model. -
James Chadwick
Chadwick confirmed that nutrons exsist, but have no charge to them.Atimic Nucleus contains neutrons and positively charge protons. Chadwick did experiments showing radiation releasing a particle from an atom that was not affected by electrical feilds, so it had to be electrically neutral.
