Periodic Table & Structure of Atom

• John Dalton

  Created the atomic theory
• Dalton's atomic theory: same elements are alike, different elements are different in mass and sizes
• Atom

  A very small particle of matter (cannot split)
• J.J. Thompson

  Discovered electrons (negatively charged)
• J.J. Thompson's model

  Plum pudding model - continuous positive charge containing scattered negative charges
• Ernest Rutherford

  Discovered the proton
• Rutherford's model

  Atom is mostly empty space with a small, positively charged nucleus in the centre, surrounded by electrons
• Rutherford's gold foil experiment

  Fast moving positively charged particles shot at gold foil, some reflected back (alike charges repel)
• Niels Bohr

  Discovered the shell/electrons, modified Rutherford's model
• Bohr's model

  Shells of electrons orbiting the nucleus (protons)
• Erwin Schrödinger

  Used quantum mechanics to explain the electrons' orbital
• James Chadwick

  Discovered neutrons and the nucleus
• Chadwick's model: neutrons are just there for mass
• Summary of atomic models

  • John Dalton created theory
  • J.J. Thompson discovered electrons
  • Ernest Rutherford discovered proton
  • Niels Bohr modified Rutherford's model
  • Erwin Schrödinger explained electrons' orbital
  • James Chadwick discovered neutrons
• Metals

  • Shiny, malleable, good conductors, ductile
• Non-metals

  • Low density, brittle, dull
• Metalloids

  • Share some properties of metals and non-metals
• Alkali metals (group 1)


  • Soft
  • Always combine with other elements in nature
  • Very reactive
• Halogens (group 17)


  • 1 valence electron
  • Very reactive, diatomic non-metals
  • Always found combined with other elements in nature
• Noble gases (group 18)


  • Full valence shell, stable group
  • Non-reactive (inert)
  • Odorless, colorless, tasteless
• Define an atom

  The smallest particle of an element that can exist
• Define an element

  A substance made of only one type of atom