ATOM


  • The word ATOM coined by OSTWALD
  • ATOM discovered by John Dalton
  • ATOM theory was proposed by John Dalton
  • Fundamental particles of an atom
  • Proton, Neutron, Electron
  • The center of an atom is called Nucleus
  • Protons and neutrons (Nucleons) are contained in the nucleus
  • Electrons revolve around the nucleus in the orbits or energy shells
Discovery

Electron (-ve)   J J Thomson
Proton (+ve)   Ernest Rutherford
Nucleus (+ve)   Ernest Rutherford
Neutron (no charge)   James Chadwick

Nobel Price
JJ Thomson1906
Ernest Rutherford      1908
Chadwick1935

Atom models
Plum pudding modelJ J Thomson
Planetary modelRutherford
Orbital model Neils Bohr
Wave mechanical model      Schrodinger

  • Most accepted atomic model is the Bohr model



  • Maximum number of electrons in a shell is 2xn2

  • The number of protons present in an atom is called its Atomic Number.
  • Atomic number is denoted by Z.
  • Number of protons and electrons in an atom is equal
  • The total number of protons and neutrons present in the nucleus of the atom is called Mass number (A).