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Democritis's Discovery 400 BC
Though the exact year is unknown Democritis, a European philosopher, stated a theory that matter was made of small particles that he called atoms. -
Cell Was Discovered.
The first cell was dicovered by Rober Hooke. -
Dalton's Discovery.
John Dalton, an English chemist, suggested that matter was made of small particles called atoms. According to Dalton's theory, atoms of the same element are identical to each other but different than the atoms of different elements. Dalton also suggested that chemical reactions consist of rearraging atoms. -
First Period Table.
First periodic table was introduced by chemist Dmitri Ivanovich Mendeleev. -
Joseph Thompson
Thompson made a "Plum Pudding" model and made the first Cathode Ray where in canal rays (psotive charge) showed up in different colors where as the cathode rays (negative charge) all showed up identically no matter what the element. -
Ernest Rutherford
Rutherford created a nuclear model of an atom in which a very small positively charged nucleus contained most of the mass od the atom, the nucleus had posistively charged protons and negatively charged electrons. He then made the discovery that there had to be a neutral particle so the electrons and protons wouldn't repel each other. He called it the neutron. -
Niels Bohr
Neils Bohr introduced a model of the Hydrogen atom in which he declared that electrons move around the nucleus in an orbit, electrons can jump up and down fron smaller to larger orbit depending on the energy they gain or lose and that electrons can only exist in certain energy levels.
