a A compound always has the same relative amounts of the elements that Chapter 2 Chem 107 1 Law of Definite proportions compose it b Joseph Prouts 2 Dalton s Atomic Theory a All matter is composed of small indivisible particles called atoms b All atoms of a given element are identical both in mass and in chemical properties However atoms of different elements have different masses and different chemical properties c Atoms are not created or destroyed in chemical reactions d Atoms combine in simple fixed whole number rations to form compounds 3 J J 4 Ernest Rutherford a Discovers the electron with the cathode Ray tube b Plum pudding model of the atom shoed the electrons in a model of an atom a Discovered the nucleus by shinning alpha particles through a gold foil i Most of the beam went through but some reflected back because it was positively charged and was large enough but also very rare 5 Millikan 6 Isotopes a Mass of electron via oil drop experiment a Have same of protons but different of neutron b Gives each isotope a different mass size 7 Protons and neutrons are located in the nucleus while electrons rotate around the nucleus 8 Elements in the same group have similar properties 9 Nobel gasses are very stable that don t react with other elements in nature 10 Alkali metals are very unstable