observing surface of atom by STM 

 REVISION

  • Dalton was first to state that the samallest indivisible portion of matter is atom .
  • Dalton's atomic theory was full of defects but it was window for modern atomic theory.
  • Atom is the smallest portion of matter which can take part in chemical combination .  It may or may not exist independently.
  • Scanning tunneling microscope can be used to have pictorial view of atom.
  • Cathode rays were discovered by J.J.Thomson with the help of discharge tube .
  • Cathode ray consists of negatively chrged particle called electron .
  • Anode rays are discovered by Goldstein .
  • Proton is not fundamental particle like electron.
  • Thomson's model of an atom is known as resin pudding model.
  • According to Rutherford nucleus of an atom contains all  protons.
  • According to Rutherford  all electrons are present in extra nuclear space .
  • Bohr proposed the concept of stationary shell.