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460 BCE
Democritus's theory of the universe
Democritus was a greek Philosopher who first came up with the term atom, which means indivisible in greek. As he believed you could divide a substance down to a point where you could no longer divide the substance, an indivisible point. The fundamental basic unit. He was mocked for his theories as the common consensus was that there were only four elements of wind, water, earth and fire. He lived from 460BCE-370BCE. -
460 BCE
Democritus's atom
Democritus theorized that all matter consists of atoms which are too small to be seen, that the atoms were solid and surrounded by empty space, the atoms had no internal structure and that each atom was different in size, weight and shape. -
John Dalton atomic theory
John Dalton was a British chemist who was the first person to adapt Democritus's theory by creating a model. He stated that all matter consists of tiny particles called atoms which were indestructible and unchangeable. That elements were different due to the weight of their atoms and that when atoms react it is the act of their atoms combining to form new compounds. -
J.J. Thomson's plum pudding/ chocolate cookie model
Thomson was a British Physicist who discovered the electron through the used of a cathode ray tube which is a vacuum tube that produces images on a fluorescent screen when shot with electron beams. This lead Thomson to propose a cookie model of the atom where negative electrons were embedded in a positive mass. as the beam would be deflected by a negative charge due to the beam being a positive charge. -
Ernest Rutherford's planetary model
Rutherford was a new zealand physicist gold foil experiment was when he fired alpha particles which are positively charged at gold foil. he measured the amount of deflection only to find that most of the particles did not deflect at all, only some particles reflected here and there. he concluded that the center was positive. He called the center the nucleus. Rutherford's model would be based off of planetary models with the negative electrons orbiting around the nucleus in a wide orbit. -
Niels Bohr
Bohr a danish physicist who built off of Rutherford's model, he established that the electrons have a set size and energy, that the lower the electron the lower the orbit, When electrons fill up the orbitals they fill the lower energy level first, meaning when a a level is filled a new level will begin. He also established that when an electron moves from one level to another radiation is created -
Erwin Schrödringer's uncertainty principle
Schrodinger discovered that electrons do not travel in an exact orbit that there location is uncertain but their general location is known as we can predict where there will be.With the probability of the orbit dependent on the energy level.
