Isotopes and relative atomic mass

• Atomic number


  The number of protons in the nucleus of an atom
• Mass number


  The total number of protons and neutrons in the nucleus of an atom
• Elements consist of atoms with the same atomic number
• Atoms can have different numbers of neutrons, forming isotopes of the same element
• The relative atomic mass of an element takes into account the different masses and abundances of its isotopes
• What are the two isotopes of carbon mentioned?

  Carbon-12 and Carbon-13
• How many protons does carbon-12 have?

  6 protons
• How many neutrons are in carbon-13?

  7 neutrons
• What is the formula to find the number of neutrons?

  Mass number minus atomic number
• What does relative atomic mass represent?

  Average mass of all isotopes of an element
• What is relative abundance?

  Amount of each isotope compared to total
• How do you calculate the relative atomic mass of chlorine?

  1. Multiply mass of each isotope by its relative abundance.
  2. Add those values together.
  3. Divide by the sum of the relative abundances.
• Why do relative atomic masses not usually come out as whole numbers?

  Due to averaging isotopes' masses and abundances
• How many isotopes of chlorine are mentioned?


  Two isotopes
• How does the relative abundance of chlorine isotopes affect its relative atomic mass?

  It influences the average mass calculation