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• The atom – Picture, parts including charge and location • Chadwick – Discovered the… • Rutherford – Gold Foil Experiment • JJ Thomson – Cathode Ray Tube • Millikan – Oil Drop experiment • Dalton – Dalton’s Atomic Theory • Democritus – His 5 ideas • Aristotle – Link with nature (Figure 4-1) History of Atom Flip Book History of the atoms 1. 2. 3. 4. 5. Matter is composed of empty space through which atoms move Atoms are solid, homogeneous, indestructible, and indivisible Different kinds of atoms have different sizes and shapes Differing properties are due to the size, shape and movement of atoms Changes in matter result from the changes in groupings of atoms 1. Matter is composed of air, fire, water, and Earth His popularity allowed his ideas to persist into the 1800’s. Dalton’s Atomic theory 1. All matter is composed of extremely small particles called atoms 2. All atoms of a given element are identical 3. Atoms can not be created, divided, or destroyed (Law of Conservation of Mass) 4. Different atoms combine in simple whole number ratios to form compounds (Law of Definite Proportions) 5. In a chemical reaction, atoms are separated, combined, or rearranged Unlike Democritus, Dalton proved his ideas with science experiments. Subatomic Particles • JJ Thomson – Found charge to mass ratio of electron – Proved atoms were divisible into smaller subatomic particles—Big Shock to Science Community – Cathode Ray Tube – Would later create the Plum Pudding Model Subatomic Particles • Millikan – Oil drop experiment – Found the charge of one electron – Electron charge = 1.602x10-19 coulombs – Accepted as -1 charge Subatomic Particles • Ernest Rutherford – Gold Foil Experiment • Shoot positive particles at gold foil Subatomic Particles Ernest Rutherford – Gold Foil Experiment • Found that most positive shots went straight through but some bounced back 1. Atom was largely empty space through which electrons moved 2. Atoms contained tiny dense region called a nucleus that contained most of the mass An atom the size of two football fields would have a nucleus the size of a nickel Subatomic Particles • Chadwick – Discovered the neutrons – Neutrons act to separate the + protons so that they don’t repel each other Atom Smallest particle of an element that retains the properties of the element