Atomic Theories

ATOMIC THEORIES AND HISTORY * Democritus (Greek) - “atomus” meaning indivicible * Indivisible particles called atoms * John Dalton – MODERN ATOMIC THEORY: 1. All matter is made of tiny, indestructible particles called atoms (Democritus) 2. All atoms of a given element are identical (not accepted today bc isotopes) 3. Atoms are neither created nor destroyed in chemical reactions (Lavoisier) 4. Atoms of different elements form compounds in whole number ratios (Proust) * J.J. Thompson (1897) – PHYSICIST WHO DISCOVERED ELECTRONS (e-) * The cathode ray * “plum pudding model” aka Chocolate Chip Cookie or Blueberry Muffin Model of an atom with electrons * Ernest “radioactive man” Rutherford (1907) – “gold foil experiment” * Electron cloud theory * Discovered that the nucleus has a positive charge * Most of the atom is empty space * Neils Bohr – planetary model (2D) worked with hydrogen * Worked with Rutherford * Electrons have specific orbitals where they travel (n) * Attraction of the positive nucleus to the electron * Erwin Schrodinger (1927) – described atom and its particle behaviour through mathematics * Heralded “quantum physics” * electrons as wavelengths, not particles * 3D description of an atom * It is possible to predict where electrons would probably be found but impossible to predict EXACTLY where you could find them * “wave function” a mathematical function * James Chadwick – discovered the particle neutrons * Werner Karl Heisenberg – “Quantum Theory” * Probabilities of electron’s behaviour and location in each orbital UNCERTAINTY PRINCIPLE – impossible to know both the momentum and the position of any object * You can know either where an object is or where it’s going but not at the same time * Probability Distribution – sprinkler