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Democritus's Theory
(300B.C.E) Democritus claims that atoms are invisible particles. He claims that they are the smallest particles of life. Atomos (in ancient Greek) means "that which cannot be further broken down into smaller pieces", this is where the term atom came from -
Dalton's Theory
Dalton invented the solid sphere model. He claimed that atoms were solid indistructible spheres, similar to billiard balls.He also talks about how atoms combine to form molecules. Dalton did not say anything about the nucleus, isotopes, or other subatomic particles. -
J.J. Thomson's Theory
Thomson came up with the "plumb pudding" model. In this model, atoms are solid spheres made-up of a positive mass with tiny negative particles embedded in the positive core. Thomson talks about the existance of protons and electrons, but did not talk about nuetrons. -
James Clerk Maxwell's Theory
Maxwell predicted that any system in which a charged particle orbited an oppositely charged particle, a light would emit at a frequency closely related to the orbiting particle's raidus. His law was established at the same time Rutherford proposed his theory -
Max Planck's Theory
Planck used the equation is E=Nhf to discover energy. Energy appeared to be emitted in wavelengths, discharging in small packets. This new theory of energy revolutionized physics and opened the way for Albert Einstein's theory of relativity. -
Rutherford's Experiment
Through his famous gold-foil expariment, he proved the atom had a dense but small positive core, he also proved that the electrons were far from the nucleus, and the electrons were separated from the nucleus by of empty space. He proposed that atoms were really just empty space. Still to this point no scientist had any proof of nuetrons in the nucleus. -
Albert Einstein's Theory
Einstein did not only theorize that atoms existed, but he proved it. He used quantum physics to explain the photoelectric effect and Brownian motion, which ultimately led to evidence that atoms exist and even showed how atoms are structured. -
Neils Bohr's Theory
Bhor proposed that electrons could be found in definite energy levels around the nucleus. He used atomic spectra to prove this. Bhor did accomplish how and where electrons are placed near a nucleus. -
Aston's Theory
Aston discovered isotopes using a mass spectrograph. A mass spectrograph is a device that detects particals photographically. This helped him discover isotopes found in a lot elements. -
Luis De Broglie's Theory
Broglie's proposed that electrons under certain conditions could behave as waves. This finding helped scientists understand that the atom could not behave like the solar system because electrons do not move in orbits. -
Erwin Schrodinger's Theory
Schrodinger used math equations to describe the likeliness of finding an electron in a certain position. His atomic model is known as the quantum mechanical model, This model predicts the odds of where an electron can be found -
Fermi's Experiment
Fermi conducted the first chain reaction by relasse energy from an atom's nucleus. He did this by using nuclear fission which is when a heavy nucleus splits spontaneously causing the release of energy. This led to the building of the atomic pile.
