Atoms and elements

• Atoms

  
• Atomic mass-number of nucleons(protons and neutrons)
• An ion is a charged particle
• An element is a substance made up of only one type of atom
• A compound is a substance made up of two or more different elements chemically combined.
• Development of the atom

  
• Isotopes are atoms with the same number of protons but different numbers of neutrons
• Relative atomic mass = isotope abundance x isotope mass number/100
• A mixture consists of two or more elements or compounds not chemically combined together
• Mixtures - Air, sea water, cement, steel

  Compounds - Carbon dioxide, silicon dioxide, water
• Mixtures can be separated by physical processes and no new substances are made
• Physical processes


  -Chromatography

  -Crystallisation

  -Simple Distillation

  -Fractional Distillation

  -Filtration
• Distillation separates liquid mixtures based on the different boiling points of the components

  The mixture is heated (by the bunsen burner) and cooled (by the condenser)
• Democritus(500 BC)->John Dalton(1800's)->JJ Thompson(1897)->Ernest Rutherford(1909)->Niels Bohr(1913)->Ernest Rutherford(1913)->James Chadwick(1932)
• Democritus- Atoms were tiny spheres
• John Dalton- Atoms are solid spheres that cannot be divided into smaller particles.
• JJ Thompson- plum pudding model, electrons orbit the nucleus in shells, electrons can only move in certain directions
• Ernest Rutherford- discovered the nucleus and the neutron.
• Neils Bohr- proposed that electrons orbit the nucleus in shells.
• Ernest Rutherford- protons
• James Chadwick- Neutrons