Elements, Isotopes & Relative Atomic Mass

• What is an element?

  A substance made up of only one type of atom, so where all the atoms of a substance have the same number of protons
• Approximately, how many different elements are there?

  100 different elements
• What is an isotope?

  Different forms of the same element, which have the same number of protons but a different number of neutrons
• How do the isotopes carbon-12 and carbon-13 differ from each other?

  They have a different number of neutrons. Carbon-12 has 6 neutrons, whilst carbon-13 has 7 neutrons
• What does relative atomic mass mean?

  Average mass of an element's isotopes
• What is the formula for relative atomic mass?

  Relative atomic mass (Ar) = (isotope abundance x isotope mass number) ÷ sum of abundance of all isotopes
• What is an element symbol?

  One or two letter abbreviation for a chemical element’s name. For example:

  H - Hydrogen

  C - Carbon

  He - Helium

  Na - Sodium