Relative Atomic Mass

• Relative atomic mass


  The weighted average of the mass numbers of an element's isotopes, based on their abundance
• Calculating relative atomic mass

  1. Mass number of isotope 1 x percent abundance of isotope 1

  2. + Mass number of isotope 2 x percent abundance of isotope 2

  3. / 100
• Relative atomic mass of boron calculated using the formula is 10.8, but rounded up to 11 on the periodic table
• Relative atomic mass of magnesium calculated using the formula is 24.3, but rounded down to 24 on the periodic table