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Period: 460 BCE to 370 BCE
Democritus
Democritus was a genius for his time. He was the first person to think up the idea of atoms. He said that everything we see including themselves were composed of atoms. His hypothesis was almost spot on, he even included that between them was empty space. His hypothesis was challenged and overthrown by a man named Aristotle, and his theory was that everything was made of four elements (Earth, Fire, Water, and Air). -
Period: to
John Dalton
John Dalton was a scientist who added on to atomic theory. He said that atoms cannot be destroyed nor created. He concluded that atoms of the same element are identical. In a chemical standpoint, Dalton was correct. An atom is the smallest particle needed to take part in a chemical reaction. However, atoms can be broken down into smaller particles called protons, neutrons, and electrons. -
Period: to
JJ Thompson
Thompson discovered the electron and that they are negatively charged. He discovered this by experimenting with gas dicahrge tubes. The cathode rays moved from the negative end to the positive end. Using knowledge that things of opposite charges attract, he concluded that the rays were made of something that had a negative charge, the electron. -
Period: to
Ernest Rutherford
He discovered something absolutely magnificent while doing an experiment we commonly refer to as, "Rutherford's Gold Foil Experiment". He discovered the nucleus and its charge. He shot alpha particles at a thin sheet of gold foil. Most of the particles shot right through it, however some of them didn't do this. Some were deflected back towards him or in another direction. This means that there was something solid blocking the path. He concluded the nucleus was positive. -
Period: to
Niels Bohr
Bohr was known for constructing a model of the atom that was very closely related to our solar system. He described the electrons as to orbit the nucleus, as Eart orbits the Sun. He also stated that all electrons have different energy levels due to their distance away from the nucleus. These energy levels can hold different electrons as well. Level two being ale to hold two electrons, level two with eight, level three with eighteeen, and level four with thirty two. -
Period: to
Schrödinger and Heisenberg - Quantum Mechanics
Heisenberg decided that quantum mechanics should be included into atomic theory. This was soon approved and Schrödinger decided to do something with it. He took Bohr's model a little further with quantum mechanics. With this new integration on equations became apart of atomic theory, he was able to predict where an electron may be around an atom. A more accurate guess if you will.
Schrödinger - Aug 12, 1887 - Jan 4, 1961
Heisenberg - Dec 5, 1901 - Feb - 1,1976