C1 - Atomic structure

• Protons


  • relative charge = +1
  • relative mass = 1
• Neutrons


  • relative charge = 0
  • relative mass = 1
• Electrons


  • Relative charge = -1
  • Relative mass = 0 (negligable)
• Atomic number


  Number of protons
• Mass number


  number of protons and neutrons
• • Electrons in an atom are placed on fixed shells
  • You can put:
  • up to two electrons in the first shell
  • eight electrons each in the second and third shells
• Isotopes


  • atoms of the same element can have a different number of neutrons, giving them a different overall mass number
  • atoms of the same element with a different number of neutrons are called isotopes
• Ions


  • atoms can gain or lose electrons to give them a full outer shell
  • Ion - a charged atom
  • atoms with more electrons than protons have an overall negative charge
  • atoms with more protons than electrons have an overall positive charge
• Relative atomic mass


  The average mass of an element
• Abundance


  the percentage of atoms with a certain mass
• Elements


  • substances made of only one type of atom
  • each atom of an element will contain the same number of protons
• Compounds


  • different types of atoms chemically bonded together
  • atoms in a compound have a different number of protons
• Mixtures


  • two or more elements or compounds not chemically bonded
  • the substances in a mixture can be separated using physical processes
  • these processes do not use chemical reactions
• Separating mixtures

  • filtration - insoluble solids and a liquid
  • crystallisation - soluble solid from a solution
  • simple distillation - solvent from a solution
  • fractional distillation - two liquids with similar boiling points
  • paper chromatography - identify substances from a mixture in a solution
• Filtration

  • separates insoluble solids from the liquid
  • pass the solvent through filter paper
  • the solvent will pass through, leaving the insoluble solid on the filter paper
• Crystallisation


  • separates soluble solids from a solution
  • heat the solvent in an evaporating dish
  • stop heating when small crystals begin to appear around the edge
  • leave the rest of the solution to evaporate
  • the solid is left as crystals