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100
Democritus (400 BC) Timetoast does not allow dates befear 100
Democritis is best known for making the theory that all matter is consisted of invisible particles. His theory was not based from experimental data, it was based on logical thinking. It is not certain the exact years that Democritus' was alive, but it is assumed that he lived in between the years on 460 and 360 BC. -
Period: 100 to
Atomic Time Line
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Antoine-Laurent Lavoisier.
Lavoisier proposed the law of conservation of mass. It states that the atoms of an object cannot be created or destroyed. They can only be moved around and changed into different particles. -
Joseph Proust
Proust was a French chemist who proposed the law of definite proportions. The law stated that a chemical compound has a set proportion of elements by volume regardless of the amount of the compound. -
J. J Thomson
Thomson showed that atoms were made of smaller atoms with charges. He did an experiment called the cathode ray tube experiment. In this experiment, he sent electricity through a cathode ray tube and the gas glowed. This experiment showed that the rays must have a -- charge since they bent towards the + side of the magnate. Thomson named the rays electrons and stated that all atoms have electrons and protons to even out the charges. Proposed the plum pudding model. -
John Dalton
Dalton came up with the first atomic theory .It had four ideas, he stated that all elements are composed of micro sized unbreakable particles also known as atoms. Atoms of the same element are the same and atoms of different elements are different. Compounds have the same relative number and types of atoms. Also, chemical reactions only involve a different arrangement of atoms. Not all of Dalton's theories were correct. His theory lead to the spherical model ( model of the atom). -
Max Planck
Max Planack proposed the Quantam Theory in 1900. The theory describes the behavior of particles or energy state based on the assumed information that energy is divided into different amounts and that matter has wave properies. -
Rutheford
Rutherford conducted the gold foil experiment in 1911. He shot alpha particles through thin gold foil and expected that most of the atoms would only be deflected slightly as they hit the gold foil. Most of the particles in the experiment blasted straight through the gold foil. He concluded that the nucleus is small consisting of empty space. He also concluded that the nucleus is dense and positively charged. He made the nuclear model which is a model of the nucleus. He discovered the proton. -
Niels Bohr
Bohr stated that electrons moved like planets. He said that electrons move around the nucleus in specific paths. He also stated that electrons can jump from one level to another. Bohr created models ( Bohr model ) and it is a model of every element and it shows where every electron, neutron, and proton is located. -
Schrodinger
Schrodinger created the Quantum mechanical model in 1913. The model showed the distribution of electrons and showed how they are almost always found in the electron cloud. -
Heinsburg
Heisenburg in 1927 stated the uncertainty principle. It stated that it is impossible to make measurements to the position and momentum of a subatomic particle with one hundred percent accuracy. -
James Chadwick
Chadwick confirmed the exsistance of the neutron proposed by Thomson. He modified the nuclear model. -
Period: to
Atomic Time line
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Steven Wienberg
Weinberg in around 1967 came up with the electroweak theory. The theory stated that the electromagnetic and the weak forces are the same at extremely high energy levels. This electroweak theory was confirmed by particle accelerator experiments in 1973.
