yr10 chem

• Element


  Contains only one type of atom
• Compound


  Substance made from two or more different elements chemically joined (i.e. bonded) together
• Mixture


  Substance made of two or more different elements and/or compounds not chemically joined together
• Types of substances


  • Element
  • Compound
  • Mixture
• John Dalton


  • Used experiments to suggest substances were made up of tiny spheres called atoms, which could not be divided
• Ernest Rutherford


  • Based his suggestions on the Gold Foil / Alpha particle Experiment conducted by Geiger and Marsden
  • Suggested that the positive charge (protons) are found concentrated in a central part of the atom, its nucleus

  
• J.J. Thompson


  • Suggested the 'plum pudding' model– tiny negatively charged electrons embedded in a cloud of positive charge
• Niels Bohr


  • Suggested electrons orbit the nucleus at set distances (i.e. energy levels)

  
• James Chadwick


  • Discovered the neutron. This supported Rutherford's proposal
• All substances are made up of atoms – the smallest indivisible particles that make up matter
• Atoms are made of protons, neutrons and electrons

  
• Protons and neutrons are found in the nucleus (the centre of the atom)

  
• Atomic number


  Number of protons in an atom
• Mass number


  Number of protons + number of neutrons in an atom
• Number of electrons = number of protons in an atom
• Energy levels (shells)


  Regions around the nucleus where electrons are found

  
• Subatomic particles


  • Proton
  • Neutron
  • Electron
• Isotopes

  Atoms that have the same number of protons (atomic number) but a different number of neutrons (mass number)
• Ions

  • Charged particles
  • Negative ions are formed when electrons are gained
  • Positive ions are formed when electrons are lost