UNIT 2: Atomic Theory

• Democritus


  matter can be broken down into its smallest particles called atomos.
• John Dalton


  initiated the development of atomic theory.
• Atom is the smallest particle of an element.
• Atomic Theory


  > Matter is made up of atoms.

  > All atoms of a given element are alike.

  > Atoms enter into combination with other atoms to form compounds.

  > Atoms can combine in simple numerical ratios.
• Subatomic Particles


  Protons, Neutrons, Electrons
• Inside the nucleus

  Protons, Neutrons
• orbits around the nucleus

  Electrons
• Atomic Number is the # of protons in the nucleus.
• Different elements have different atomic #s

  True
• Mass Number is the total number of protons and neutrons.
• Isotopes has the same atomic # but different # of neutrons.
• Mole is the amount of substance that has the same mass as 12g of carbon-12.
• Avogadro's Number is the # of atoms in 12g of C-12.
• 1 mole

  6.022x10^23
• mass of one mole of a substance

  Molar Mass
• true formula of the molecules

  Molecular formula
• simplest chemical formula

  Empirical Formula
• J.J. Thompson


  discovers electrons by plum pudding model
• Ernest Rutherford


  electrons move around the nucleus.
• Bohr Model


  electron moves in a circular orbit at fixed distances from the nucleus.
• James Chadwick


  confirms the existence of neutrons
• Erwin Schrodinger


  Electron Cloud Model