2.1.1 (Atomic structure and isotopes)

• Isotopes:

  Atoms of the same element with different numbers of neutrons and different masses.
• Atomic structure:

  Subparticles include: protons, neutrons, and electrons.
• Atomic number:

  The number of protons (which is the same as the no. of electrons) in the atom.
• Mass number:

  The total number of protons and neutrons in an atom of the element.
• Ions:


  An atom which has lost or gained electrons making the atom have an overall charge of either positive or negative.
• Relative isotopic mass:

  The mass of an atom of an element compared with 1/12th of the mass of an atom of carbon-12.
• Relative atomic mass:

  The weighted mean mass compared with 1/12th of the mass of an atom of carbon-12
• Standard for atomic masses:

  Carbon-12.
• Use of mass spectrometry:

  1. Determining the relative isotopic masses and proportions of each isotope.
  2. Calculating the relative atomic mass of an element based on the relative proportions of its isotopes.
• Mr (relative molecular mass):


  The sum of the relative atomic masses of each atom within the molecule.