Isotopic Abundance & Relative Atomic Mass (CIE A Level Chemistry)

• Isotopes are different atoms of the same element that contain the same number of protons and electrons but a different number of neutrons.
  • These are atoms of the same elements but with different mass numbers

• Because of this, the mass of an element is given as relative atomic mass (A_r) by using the average mass of the isotopes
• The relative atomic mass of an element can be calculated by using the relative abundance values
  • The relative abundance of an isotope is either given or can be read off the mass spectrum

Worked example: Calculating relative atomic mass of oxygen

Answer 

The correct answer is 1

= 16.0044

= 16.00

Worked example: Calculating relative atomic mass of boron

Answer