Atomic Theory

Atomic Theory

  • Antoine Lavoisier
    • Father of Chemistry, Law of Conservation of Mass
  • Proust
    • Law of Definite Proportions
    • There is always a ratio by mass if one has a particular compound

John Daulton (1803)

  • 1st Atomic Theory

  

  1. All matter is composed of tiny invisible particles

      1. Named “atoms”

  1. Atoms of the same element are alike
  2. In a chemical reaction, atoms are separated, rearranged, and joined
  3. Atoms combine in single-number ratios
Law of Multiple Proportions
  • If two elements can combine in more than one way, each compound.
Subatomic Particles
  • neutrons (O charge), discovered by Chadwick, one atomic mass unit (amu)
  • protons (+ charge), discovered by Goldstein, 1 amu
  • electrons (- charge), discovered by Thompson, 0 amu
  • isotope - atoms of some elements with different numbers of neutrons
  • ion - charged particle
    • gain electron - negative charge
    • lose electron - positive charge
    • cation - positive ion
    • anion - negative ion
Average Atomic Mass
  • the weighted average of the masses of isotopes
    • weighted by abundance

Miscellaneous

  • electron cloud - spaces around the nucleus where electrons are found
  • nucleus - protons and neutrons; positive
  • mass number - protons and neutrons
  • atomic number - number of protons
Determination
  • element - determined by protons
  • isotope - determined by neutrons
  • ion - determined by electrons