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Period: to
Atomic theory
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Dalton
John Dalton proposed the atomic theory, stating that everything as made of atoms. At that point in time, the atomic theory said that 1) All matter is made of atoms that can be combined, 2) All atoms of the same element are exactly alike, 3) Atoms of differeny elements are different, and 4) Atoms of two or more elements can be combined to for a new substance. Although his model of the atom was just a simple circle, he was correct about most of these hypothesises. -
Crookes
Crookes proved the existence of electrons. He did this by reconstructing a Cathode ray. What he did was put black vanes on one side and silver on the other. This caused the vacuum tube to spin whenever light hit it. After the experiment, he pulled some objects out from the tube that had a negative charge. It caused the objects to spin which proved they had mass, therefore proving the existence of electrons. -
JJ Thompson
He discovered that atoms weren’t simple solid spheres. Also furthered the work of Crookes and made it obvious that electrons existed. -
Rutherford
While Rutherford was expirimenting with uranium and thorium, he discovered two different radiations. He called them alpha and beta particles. -
Rutherford
In 1911, Rutherford conducted an experiment where he shot alpha particles at a gold sheet. Most of them passed through, leading him to conclude that atoms were mostly made of empty space. However, very few bounced back, allowing him to discover the nucleus. He concluded that it was a small, dense area in the center of the atom. -
Bohr
Bohr proposed that electrons move around the outside of the nucleus in energy levels and have a fixed amount of energy. The farther away from the nucleus the electron is, the more energy it has. When an electron loses or gains energy, it can move between energy levels. -
Heisenberg
He believed that if people wanted to hypothesize about atoms, they would have to observe them. His best-known work is the creation of the uncertainty principle, which says that our knowledge of the atom is limited because of certain phenomena of the atom, such as short wave radiation. -
Schrodinger
He created the quantum mechanical model of the atom after seeing Bohr’s model of the atom. He used mathematical equations to be able to predict where an electron was in its orbit. His model of the atom introduced sub-energy levels. -
Chadwick
He took beryllium atoms and bombarded them with alpha particles. When he noticed the atoms giving off an unknown radiation, he hypothesized that it was being given off because of a neutral particle in the middle of the atom. Because of this, he discovered the neutron.
