reviewer

• Plato: 'concept of atom having geometric shapes'
• Democritus: 'Atoms being separated by empty space'
• Leucippus: 'Atoms are indivisible unit of matter'
• Aristotle: 'Balance between 4 elements can be obtained'
• Phosphorus was the 1st element to be discovered in a serendipity way
• John Dalton


  British teacher in late 17's, combined the ideas of elements by ancient Greek philosophers with that of atoms
• Dalton's Atomic Theory


  • 1. All matter is made of tiny indivisible particles called atom
  • 2. Atom of the same elements are identical
  • 3. Atoms combine to form compounds in simple whole number ratio
  • 4. Chemicals reactions involve the rearrangement of atoms; no matter is created nor destroyed
• Billiard Ball Model


  Subatomic particles: Proton +, electron -, and neutron o
• Michael Faraday


  • 1. Matter must contain positive and negative charges
  • 2. Opposite charges attract, like charges repel
  • 3. Atoms combines to from compounds because of their attraction to one another
• J.J. Thompson


  • 1. Atoms contains electrons
  • 2. Electrons have very little mass and have negative charge
  • 3. The rest of atom is positive
  • 4. Electrons are stuck throughout the atom randomly
  • 5. Electron can be added or removed to give positive or negative charges
• Earnest Rutherford


  • 1. The nucleus contains all the positive charges and most of the mass
  • 2. Nucleus is tiny compared to the rest of atom
  • 3. Electrons orbit the nucleus like plates around the sun
  • 4. Mass of electron is 1/1800th the mass of proton
  • 5. Size of atom determine by the furthest electron form the nucleus
  • 6. Only empty space between nucleus and the electrons
• James Chadwick discovered neutrons
• Marie Curie


  • Coined the term 'RADIOACTIVITY'
  • Died because of radiation from elements like uranium
  • Discovered Polonium and Radium
  • Nobel prize for Physics and Chemistry for her works
• Niels Bohr


  • 1. Electrons orbit around the nucleus
  • 2. Electrons can exist at a given energy levels
  • 3. Energy level is where an electron is likely to be moving
  • 4. The nucleus contains the proton and neutron, almost all the mass
  • 5. Electron Cloud is most of the volume of an atom, where electrons can be found