History of the atom

• Greeks


  • matter
  • indivisible
• De Broglie


  • wave particle duality
• Dalton


  • All matter is made from atoms
  • Atoms are indivisible
  • They cannot be created or destroyed
• Cathode


  • neg. end of battery
  • Vacuum tube
  • Shadow
• Chadwick


  • Discovered neutrons
  • Alpha particles and berylium
• Thomson


  • ELECTRON
  • Plum pudding
  • Cathode rays
  • Charged parallel plates
  • vacuum tubes
  • CATHODE RAYS ARE NEGATIVE
  • Attracted to + plate
• Rutherford


  • Gold foil experiment
  • Alpha particles
  • discovered nucleus
  • Alpha source, gold foil and fluorescent screen
  • Most went straight through- atom mostly space
  • Some deflected at large angles, came close to + nucleus. ●some rebounded on own path
• Bohr


  • e- have fixed energy bevels
  • when @ lowest- grand state
  • recieve energy (heat/electricity)
  • excited e. -higher energy level
  • temporary + unstabl
  • emit light at specific wavelength
• Milikan


  •oil drop experiment.

  • measure the charge on the electron.
• Lines in hydrogen spectrum


  Balmer- visible

  Paschen- infrared

  Lymann- ultraviolet
• Crookes


  •cathode rays- negative end of battery

  •vacuum tube

  •shadow/ fluorescent
• Chemistry: the study of matter
• Atom: smallest part of an element
• Alpha particles: are the nuclei og helium atoms produced by certain radioactive substances -> positively charged
• Continuous spectrum of light: contains all possible wavelengths of light eg colours of the rainbow
• An emission line spectrum of light: spectrum in which energy is concentrated at particular wavelengths eg coloured lines on black background.
• Energy level: fixed / definite amount of energy which an electron can have in an atom.
• Ground state of an atom: all electrons in an atombare in the lowest energy level available to them.
• Ground state of an electron is when an electron is in the lowest energy level available to it.
• Excited electron is an electron which has absorbed energy and has moved up to a higher level. This state is unstable and temporary.