C2.1.1

• Isotopes are different versions of the same element with the same number of protons but different numbers of neutrons
• Protons:

  • Abbreviation = P+
  • Mass = 1 u
  • Charge = 1+
• Neutrons:

  • Abbreviation = n
  • Charge = 0
  • Mass = 1 u
• Electrons:

  • Abbreviation = e-
  • Charge = 1-
  • Mass = 1/1836 u
• The Bohr model explains reactivity due to fixed numbers of electrons in shells
• Isotopes have the same chemical properties due to having the same electronic structure but different physical properties due to their different masses
• Define Relative isotopic mass

  the mass of an atom of an isotope compared to 1/12th the mass of an atom of carbon-12
• Define relative atomic mass (Ar)

  The weighted mean mass of an atom of an element compared to 1/12th the mass of an atom of carbon-12
• What is the abbreviation of relative atomic mass?

  Ar
• What is this a picture of?

  A Mass Spectrum

  
• What is a?

  • mass to charge ratio
  • m/z
  • mass/charge

  
• What should the mass to charge ratio of a mass spectrum be assumed to be?

  1
• What is b?

  percentage abundance

  
• For a mass spectrum of chlorine, what is c?

  75%

  
• for a mass spectrum of chlorine what is d?

  25%

  
• Ar equation

  relative atomic mass = ( mass x abundance ) + ( mass x abundance ) / 100
• What experimental method is used to calculate relative atomic mass?

  Mass Spectrometry
• Relative molecular Mass ( Mr ) is used for simple molecules and is worked out by adding together the relative atomic masses ( Ars ) of all the atoms in the molecule
• Relative formula mass is used for compounds with giant structures for example giant ionic or giant covalent and is worked out by adding together all the relative atomic masses ( Ars ) of the ions in the formula unit
• The units used to measure atomic mass are atomic mass units ( u )
• 1 u ( atomic mass unit ) = 1/12th of the mass of one carbon-12 atom
• 1u ( atomic mass unit ) = approximately the mass of 1 proton or neutron