Isotopes and Atomic Mass

• Atoms of the same element with different numbers of neutrons.

  Isotopes
• Defined by the number of protons, which remain constant across isotopes.

  Atomic Number
• The sum of protons and neutrons, which varies among isotopes.

  Mass Number
• The weighted average mass of an element's isotopes, based on their relative abundance.

  Atomic Mass
• The proportion of each isotope present in a sample.

  Relative Abundance
• What is the formula for Atomic Mass?

  Atomic Mass = Isotope Mass x Relative Abundance