Basics

Basics

1. Ideas of the atom

   • 700 BC
     • Made of 4 elemements
       • Earth
       • Fire
       • Water
       • Air
   • 1400
     • Matter made from atoms
   • 1661
     • Robert Boyle
       • Some substances can't be split into anything smaller
       • Elements, found in periodic table
   • 1803
     • John Dalton
       • Elements made of atoms, couldn't be broken down
       • Atoms of different elements = different masses
   • 1896
     • Henri Becquerel
       • Radioactivity
         • Particles come from within atoms
         • Atoms can be broken down
     • JJ Thomson
       • Discovered electron
         • Negative charge
         • Had to be positive charge in atom
         • Had to be heavy particles
       • Plum pudding model
   • 1911
     • Rutherford
       • Atom had a nucleus
       • Alpha experiment
   • 1913
     • Bohr
       • Nucleus orbited by electrons in shells of fixed energy

2. Fundamental particles

   • Protons and nuetrons
     • Form nucleus, in centre
     • Proton positive charge, neutron neutral charge
   • Electrons
     • Surround nucleus
     • Negative charge
   • Arrangement
     • Nucleons in centre, held by strong nuclear force
     • Electrons surround in shells
   • Ions
     • Lose electrons
       • Positive ion
     • Gains electrons
       • Negative ion

3. Electron arrangement

   • Ideas
     • 1913
       • Bohr
         • Like a solar system
     • 1932
       • Neutron discovered
     • 1926
       • Schrodinger
         • Electrons had wavelike properties
   • Shells
     • First shell holds up to 2 electrons
     • Second shell holds up to 8 electrons
     • Third shell holds up to 18 electrons

4. Mass number, atomic number and isotopes

   • Atomic number
     • Proton number
     • In atom, electron number also
   • Mass number
     • Number of nucleons
   • Isotopes
     • Atoms of the same element (same proton number) but different numbers of neutrons
     • Chemically identical
     • Vary in mass number
   • Carbon dating
     • Measure radioactivity level of carbon 14 and compare to the half life, find out how long ago something died