Elements

• An element is a substance made up of atoms that all have the same number of protons in their nucleus
• Elements consist of atoms with the same atomic number:

  1. Atoms can have different number of protons, neutrons and electrons.
  2. For example, an atom with one proton in it's nucleus is hydrogen and an atom with two protons is helium
  3. If a substance only contains atoms with the same number of protons it's called an element.
  4. There are about 100 different elements
• Atoms can be represented by symbols:

  • Atoms of each element can be represented by a one or two letter symbol
  • Some make perfect sense- C= Carbon, O= Oxygen, H= Hydrogen
  • Other's do not- Na= Sodium, K= Potassium, Fe= Iron
• Isotopes:

  1. Different forms of the same element
  2. Same number of protons but a different number of neutrons
  3. Isotopes have the same atomic number but different mass numbers
  4. E.G. carbon 12 has 6 protons, 6 electrons and 6 neutrons whereas carbon 13 has 6 protons, 6 electrons and 7 neutrons.
  5. There are a lot of elements that have isotopes so they use relative atomic mass rather than mass number
• 1. Calculate relative atomic mass by doing sum of (isotope abundance x isotope mass number) divided by sum of abundances of all isotopes.
• Cu 63 has abundance of 69.2% and Cu 65 has abundance of 30.8%.

  Relative Atomic Mass= (69.2 x 63) + (30.8 x 65) / 100 = 63.6 (1 d.p)