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465
B.C. Democritus
He believed that all matter was atoms and that every thing took up space whether it be air or inside a tree. He also believed that atoms of different matter had different characteristics. -
Period: to
Atomic Theory
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Dalton
Dalton thought atoms were small spheres and for all matter he thought if you broke it down enough then it would not be able to get it any smaller also he realized that some thing could separate into new things like how water turns into oxygen and hydrogen. -
Thomson
Thomson used x-rays to look inside people’s bodies and discovered negatively charged particles that he called electrons. Though Thomson did not know they were in atoms; he thought that electrons were evenly spread out like plums in pudding. He called this the plum pudding model. -
Rutherford
Rutherford conducted an experiment in which he shot alpha particles or the nucleus of an atom at a very thin foil sheet and discovered that every once in a while a particle would bounce off instead of go right through this is when he discovered that atoms have compact spheres of protons and neutrons and the rest of the space was empty -
Bohr
Bohr Conducted an experiment in which he put energy into an atom and the electrons got further away from the nucleus and when the electrons moved to different energy levels they would produce visible light. Then with this information he was able to infer electrons move around the atom the way the planets go around the moon. -
Moseley
He performed an "oil-drop" experiment, determined the charge of one electron and using the known mass-charge ratio, was able to calculate the mass on one electron (9.11x10^-28g) -
Schrödinger
He expanded the idea that electrons behaved as particles AND waves, this developed the quantum mechanical model of the atom -
James Chadwick
He discovered the neutron
