P4 - Atomic Structure

P4 - Atomic Structure

1. Models of the Atom

   • The Greeks believed that if you cut an object up enough times you'd get to a point where it becomes uncuttable
   • In 1897 J J Thomson came up with the Plum Pudding model after discovering the electron. The Plum Pudding atom is a positive sphere with negtive electrons inside it
   • In 1905 Rutherford tested the Plum Pudding with his two students. The conclusion was that there was a positive nucleus surrounded by empty space, with the electrons being further out
   • In 1913 Niels Bohr changed Rutherford's model by suggesting that the electrons orbited at specific distances from the nucleus
   • In 1932 James Chadwick proved that the theory that there was a neutron inside the nucleus alongside the protons

2. Atoms, Isotopes and Ions

   • Atoms are very small, about 1 × 10-10 metres. Each particle has it's own relative mass, protons and neutrons are 1 whilst electrons are 1/2,000
   • The number of protons defines an element, however the number of neutrons and it's mass number can differ. These are called Isotopes, for example hydrogen has 3 types, hydrogen, deuterium (hydrogen-2)