SCH3U Models of the Atom PDF

SCH3U​ ​ ​ Models of the Atom​ ​ ​ Ancient Models of Matter ​ Democritus (a Greek Philosopher) proposed that matter could be divided into smaller and smaller pieces until a single indivisible unit was reached ​ He named this indivisible particle an atom...

SCH3U​ ​ ​ Models of the Atom​ ​ ​ Ancient Models of Matter ​ Democritus (a Greek Philosopher) proposed that matter could be divided into smaller and smaller pieces until a single indivisible unit was reached ​ He named this indivisible particle an atom ​ Proposed that all matter was made up of atoms and void space ​ Did not do experimentation to draw his conclusions Dalton’s Atomic Theory (BIlliard Ball Model) ​ He used experimentation and drew these conclusions: 1.​ Matter consists of definite particles called atoms 2.​ Each element is made up of its own type of atom (ex. Helium only contains Helium atoms) 3.​ Atoms of different elements have different properties (ex. Helium has different properties than Sodium) 4.​ Atoms of two or more elements can combine in contact ratios to form new substances ​ Ex. Carbon and Oxygen can combine to form carbon dioxide (CO2) where there will be one carbon and 2 oxygens 5.​ Atoms cannot be created or destroyed, or subdivided in a chemical change Thomson’s Plum Pudding or Raisin Bun Model ​ Concluded that atoms were NOT the smallest unit of matter, there were particles within the atom! ​ Found that there were positive and negative particles with the cathode ray experiment - Thomson wanted to see if, by bending the cathode rays (beam of electrons) with a magnet, he could separate the charge from the rays. He found that when the rays entered, a large amount of negative charge was measured ​ The atom was a positively charged sphere with negatively charged particles (later called electrons) embedded within ​ The dough represents the positively charged sphere and the raisins represent the negatively charged electrons. Overall the atom is neutral Rutherford’s Model (Nuclear Model) ​ Gold foil experiment: very thin sheets of gold foil were bombarded with fast moving alpha particles. Alpha particles, a type of natural radioactive particle, are positively charged particles with a mass about four times that of a hydrogen atom. ​ Some of the particles deviated at small angles. One out of every 12,000 particles appeared to bounce. ​ Confirmed that the positive charges were concentrated in the center of the atom with negative charges surrounding the center  ​ Most of the atom is made up of empty space ​ Further work by Chadwick revealed that neutrons (have similar mass to protons but no charge) exist in the nucleus of the atom. Bohr Model (Planetary or Solar System Model) ​ Electrons move in specific orbits controlled by electrostatic forces ○​ Electrons do not lose energy while moving in any given orbit ​ Organized orbitals as energy levels (highest energy in the valence shell) Modern Atomic Theory ​ Werner Heisenberg understanding of quantum mechanics and Erwin Schrödinger application of mathematics to understand positions of elections led to the development of the modern atomic theory ​ Atoms consists of subatomic particles: electrons, neutrons and protons ​ Atoms of one element cannot be converted into atoms of another element by a chemical reaction ​ All atoms of one element have the same properties (i.e. size and mass) ​ Atoms of different elements combine in fixed proportions to form compounds