Unit 1.1

• Atoms consist of a central nucleus containing protons and neutrons
• The nucleus is surrounded by electrons in energy levels(also called shells.)
• Proton: Mass=1, Charge= +1

  Neutron: Mass=1, Charge=0

  Electron: Mass=0.0005, Charge=-1
• Atomic number=Number of protons
• Mass number = Number of protons + Number of neutrons
• Number of electrons = Atomic number
• The number of protons decide what type of atom it is
• Isotopes are atoms with the same number of protons but a different number of neutrons
• The relative atomic masses are measured on a scale on which the mass of an atom of 12C is defined exactly as 12
• I Ionisation

  Am Acceleration

  In Denial Ionic Drift

  Debating Detection

  Divorce Again Data analysis
• Ionisation - used for elements and low MR compounds, one electron knocked of to form 1+ ion
• Electrospray- used for high MR compounds, sample dissolves and injected into ionisation chamber
• Acceleration - Ions accelerated using electrical field so all ions have same kinetic energy
• Ionic drift - Ions enter flight tube, different mass=different time of flight, lighter ions are quicker
• Detection:

  • negative charged plate that produces current when atoms hit plate
  • mass of ions hitting detector detected by time of flight
  • mass spectrum shows number of particles that hit detector
• an atomic orbital - a region around the nucleus that can hold up to 2 electrons with opposite spins
• there are s, p, d and f orbitals
• every electron shell contains an s orbital
• orbitals with the lowest energy levels are filled first
• we put electrons into individual orbitals first, because electrons in the same orbital repel
• Chromium and copper are exceptions because the 3d subshell must be stable

  
• Ionisation - atoms turn into ions
• First ionisation energy - energy needed to remove one mole of electrons from one mole of atoms in their gaseous state to form one mole of 1+ ions
• Second ionisation energy - Energy needed to remove one mole of electrons from one mole of 1+ ions in their gaseous state to form one molecule of 2+ ions
• The greater the attraction between the outer electrons and the nucleus the greater the ionisation energy
• The greater the number of protons the greater the force of attraction between the outer electrons and the nucleus
• Electrons in outer shells repel electrons in inner shells, this reduces attraction between outer electrons and the nucleus