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340
Aristotle
340 BC - Aristotle didnt think atoms could be constantly moving if they were in a void. He beleived there were four elements and four qualities, and that they would align into their rightful place and be at rest. -
440
Democritus
440 BC - Beleived that if you continually cut a substance in half, eventually you would get an "uncuttable" piece. He called these uncuttable pieces particles, which means indivisible in greek.He thought atoms were hard and small particles compiled by one substance and in one particular shape. He thought they were always moving and that they combined with each other. -
Robert Boyle
1650 - He measured relationships between volume and pressure of gasses. From his expiraments he concluded that gasses are made up of tiny particles that group together to make different substances. -
Antoine Lavoisier
1765 - This man created the idea of having on single -common language for all of science to use. for example when someone called a substance iron, than everyone was to call it iron. This allowed for science to advance and for chemists to learn new properties of other metals and know how to organize them. -
John Dalton
1803 - He claimed the reason elements combined was because all elements are made up of atoms. He also published a three- part atomic theory. 1. All particles are made of atoms, they cant be divided or destroyed. 2.Atoms of the same elements are identical diferent element's atoms are different. 3. atoms join with other substances to create new and different substances. -
J.J Thomson
1897 - Change Player Size Watch this video in a new windowCathode Ray TubeJJ thomson Cathode ray tubeThomson used a cathode ray tube to inferr that there are small particles inside of every atom. This inference proved dalton's theory to be wrong. Particles can be divided. Through this expirament thomson also inferred that atoms must be negatively charged.Thomson purposed the plum pudding model which allowed scientefic advances to occur. -
Hantaro Nagoaka
In 1904, Hantaro Nagaoka developed an early but incorrect planetary model of the atom. He based his model of the atom around the rings of the planet saturn. however his model was not created properly. He explained that the rings are held there due to its massive orbit. although this model was wrong it still allowed for the discovery of the atoms rings. -
Ernest Rutherford
1909 - Ernest Rutherford's Gold Foil ExperimentErnest Rutherford's Gold Foil Experiment Chemistry Visualin his expirament rutherford shot a positively charged beam of particles through a sheet of gold foil. He thought if the particles were soft as jj thomson's plum pudding model had suggested than they would pass Through and continue in a straight line, Which most did. However some did not this showed that the plum pudding model was somewhat false, so rutherford created a new model. -
Neils Bohr
1913 - This man suggested that electrons travel around the nucleus in definite paths. These paths are always at a certain "level" away from the nucleus. He also stated that electrons cannot travel in between each path, however they can jump from one path to another. -
Quantum Mechanical Model
Now - The current day model of an atom is based on a theory of quantum mechanics. Each electron is thought of as a cloud, of negative charge, instead of one tiny negative particle. It is beleived in this model that electrons "occupy" all of the space in an atom at different levels or rings. An atom consists of energy levels, neutrons, and protons.
