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John Dalton proposed an atomic theory.
His theory was:
1) All matter is composed of extremely small particles called atoms.
2) atoms of an element are identical in size, mass, and other properties (atoms of different elements differ in size, mass, etc.) 3) Atoms cannot be subdivided, created or destroyed,
4) Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
5) In chemical reactions, atoms are combiined, separated, or rearranged. -
J.J. Thomson proposed the Plum Pudding Model for the structure and placement of electrons and protons throughout the atom.
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Robert Millikan measured the charge of the electron; this lead to the conclusionn that an atom is around two-thousandth the mass of a hydrogen atom.
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Ernest Rutherford discovered the densely packed bundle in the atom: He called it the nucleus, and he concluded that the volume of the nucleus must be extremely small compared to the rest of the atom.
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Niels Bohr proposed that electrons don't spiral into the nuclues; He said that electrons ccan only orbit certain distances from the nucleus, and energy is created when the electrons go from a high orbit to a lower one (atoms also aborb energy)
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Henry Moseley used rays to find the frequencies of many elements. This helped him to find the true atomic number. He was the founder of Mosely's law, which has to do with how the number of protons influences the atomic number.
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Francis Aston invented the mass spectrograph, and he was the first to observed isotopes.
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Wolfgang Pauli hypothesized that electrons spin while orbiting the nucleus. He also stated that not two electrons can have the same set of quantum numbers
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Louis de Broglie came up with the idea that atoms can move in wave form (matter waves).
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Erwin Schrödinger built a model to explain how atoms could move in circular waves (particle waves were in a round shape, and there are unstable and stable waves).
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Werner Heisenberg created the Heisenberg uncertainty law, which states that when someone measures the certainty of the position of an atom, the uncertainty in its momentum increases. Or that is the momentum is known, the location is hard to determine.
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Paul Dirac dscovered equations that led to the founding of a positively charged electron called the positron.
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James Chadwick dicovered the neutron, which he found was heavier than a proton
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Lise Meitner helped to verify that heavy elements capture neutrons and form unstable products which undergo fission (fission chain reaction).
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Enrico Fermi was the first to cunduct a successful chain reaction by releasing energy from atoms in the nucleus.
