Elements, isotopes & relative atomic mass

• Element

  Substance made up of one type of atom
• Isotope

  Different forms oof the same element, which have the same number of protons but a different number of neutrons
• Relative atomic mass

  Average mass of all the isotopes of an element
• What is the formula for relative atomic mass (Ar)

  Ar= Sum of (Isotope abundance × Isotope mass number)/sum of abundances of all isotopes