-
100
Democritus
Democritus was a Greek philosopher who believed that everything was made up of tiny particles that he called atoms. Democritus was the first to propose this idea in 400 BCE. This idea was adopted by the greeks for about 50 or more years, until Aristotle, who was in favor of the leader Alexander the Great, said that his idea was wrong. -
100
Aristotle
Aristotle was a greek philosopher in the 2nd century BCE. Around 335 BCE he proposed the idea that there was an infinate number of things that made up everything. Everything could be made into smaller pieces. He believed in the four elements earth, air, water, and fire. This replaced Democritus' theory of the atom, mostly because he was a teacher of Alexander the Great. -
Antoine Lavoisier
He was the first to propose the law of conservation of mass. This allowed reactions to become more predictable. This is what kick started chemistry. This allowed chemist to expiriment and lead to some of the worlds greatest discoveries. -
John Dalton
Dalton made the first model of the atom, saying that it was a solid.
He did however think that the atom was round. It was a theroy that showed how chemical compounds worked. This model was adopted for almost a century, and is what all the other scientists based their model after. -
Henri Becquerel
Becquerel was credited for the dicovery of radioactivity. He conducted an expiriment in which he exposed elements wrapped in black paper, and exposed them to sunlight, and one in total darkness. They both did the same thing, whcih is that they emitted radiation with no other source such as the sun. This allowed chemist to predict reactions better. -
Max Planck
He was a physicist in the 20th century. He did work with light and radioactivity. He created the quantum theory. It said that energy isn't infinite. Each energy band is carried in discontinueous units, and is equal to the radiation given off. This baffled scientists until it got help by Albert Einstein. This helped Bohr with is atomic model. -
Marie and Pierre Curie
They expanded on Henri Becquerel's wrok on radioactivity. Henri found that uranium was radioactive, and the Curie's found that in other elements as well. They found that the elements Polonium and Radium. They won the noble prize for this discovery. Marie wanted radioactivity to be used on cancer patients, blazing the trail for modern chemotherapy. -
J.J. Thompson
He was the first to discover that atoms had particles. He conducted an expiriment where he put a charge in a vile, and it created a beam. Then he put a magnet to the glass and it attracted the beam and bent it. He concluded that the atom was mostly positive with negative particles sprinkled in. It was often called the Plum Pudding Model. -
Robert Millikan
by performing the oild drop expiriment he proved the Thompson theory that the electron was much smaller than the proton. -
Ernest Rutherford
Ernest Rutherford was a student of J.J. Thompson. He was credited to have found the nueclus of an atom. He was trying to prove Thompson's model of the atom, and created an expiriement. He shot alpha particles at a thin sheet of gold foil. He was expecting them to shoot right through the paper, but in actuallity they bounced off and went in diffrent directions. So that proved that the postive particles were in the middle, and the electrons orbited around the positive nucleus. -
Henry Mosely
He studied the frequencies given off by x-rays. He found that the atomic number was equal to the number of positive paricles in the nucleus. -
Niels Bohr
Bohr was a student of Rutherford and wanted to prove his model to be accurate, after many physicists said his model wouldn't work. So Bohr used Rutherford's model, but used the concept of special orbit. He used the theory that was created by Max Planck, of packets of energy and each one had a certain number of electrons holding the orbit in place. (2n^2) -
Werner Heisenberg
He was a german scientist during the 1920's. Instead of looking at the atom in scientific terms, he looked at it in a mathmatical point of view. By doing this was able to calculate the movement of electrons, and was able to discover how they behaved, and that they were made up of photons. -
Erwin Schrodinger
He was an Austrian scientist. He discovered the electron cloud in the 1920's. He used the Bohr model, but instead of showing the exact path that the electron was on, it showed their location of the electrons. It ended up showing a cloud around the nucleus. -
James Chadwick
He was a scientist in the 1930's. He concluded that the neutron made up half the mass of the atomic mass.
