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Aristotle b.c
Aristotle did not believe in the atomis theory. He believed that all matter was made of the four elements; fire, earth, air and water. He was one of the greatest minds and had many followers. He gatherd most of his information from his former teacher plato and that helped contribute to his theory. -
Dalton
He explained the behavior of atoms in terms of the measurement of weight. It served a useful purpose in allowing him to abolish the idea held by many previous atomists. he called his model the "Billiard Ball Model" because he thought the atoms looked like a billiard ball from pool. -
Thomson
He discovered the electron in a series of expirements ddesigned to study the nature of electric discharge in a high vaccum cathode-ray tube, an area being investigated by numerous scientists at the time. His research in cathode rays led to his discovery. JJ Thomson thoght the atom looked like a plum pudding, this meant he thought the atom was a ball of positive charge with smaller balls of nagative charge embedded in it, he proposed this theory in 1904. -
Rutherford
he discovered that the atom was not the smallest unit if mass. the model described the atom as a tiny, dense, positively charged core called a nucleus. In which nearly all the mass is concentrated, around which the light, negative constintuents, can ekectrons, circulate at some distance, much like planets revolving around the sun. He did pizzles of the decay families of thorium, radium, etc. , but he was passing much of this work to Bollwood, Hahn,and Soddy. -
Bohr
He proposed that enrgy levels of lectrons are discrete, and that the lectrons revolve in stable orbits around the atomic nucleus, but can jump fromone energgy level to another. He contrbuted the quantum theory of atomic structure which basically states that an atom emits electromagnetic radiation only when a electron changes from one energy. He thought an atom should look like a nucleus with electrons floating randomly. He made his discovery by performing expirements on the element hydrogen -
Heisenburg and Schrodinger
Discovered allotropic forms of hydrogen and developed a theory of quantum physics. His contribution to the atomic theory was that he calculated the behavior of electrons, and subatomic particles that also make up an atom. He said that atoms bahve like both waves. -
Democritus b.c
He came up with the idea that all matter contains atoms. He reasoned that atoms were the smallest part of matter, and could not be broken down further. It is finding did not change the current atom model of his time, it just added another element. The atomic theory. He said the atom looked like a marble. He drew this from wathcing decay and mixing of the elemnts laid out of the eleatics, for instance the mixture of water and earthin mud that is not easily separated once combined
