Isotopes and Relative Atomic Mass

Isotopes and Relative Atomic Mass

1. Isotopes

   • Isotopes are DIFFERENT ATOMIC FORMS of the SAME ELEMENT, which have the SAME NUMBER OF PROTONS but DIFFERENT NUMBERS OF NETRONS
   • Isotopes must have the same number of protons but different mass numbers
   • If they had different numbers of protons they'd be different elements altogether
   • A popular pair of isotopes and "carbon-12" and "carbon-14"

2. Relative Atomic Mass

   • Uses the average mass of the isotopes of an element.
     • Has to allow for the relative mass of each isotope ands its relative abundance.
       • Relative abundance just means how much there is of each isotope compared to the total amount of the element in the world.
   • 1) multiply the mass of each isotope by its relative abundance.
     • 2) Add those together
       • 3) DIvide by the sum of the relative abundances.
   • DOn't usually come out as whole numbers or easy decimals.
   • Often rounded to nearest 0.5
     • In periodic table

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