Definitions

• Acceleration

  Second stage of TOF spectrometry

  The positively charged ions are accelerated by an electric field so that they have the same kinetic energy
• Atomic Number

  The number of protons in the nucleus
• Electron Impact Ionisation

  Method of ionisation in TOF spectrometry

  The sample is vaporised and an electron gun fires high energy electrons at it, causing an electron to be knocked off each particle to produce 1+ ions
• Electrospray Ionisation

  Method of ionisation in TOF spectrometry

  The sample is dissolved and pushed through a fine nozzle at a high pressure

  A high voltage is applied to it causing each particle to gain a H+ ion

  The sample is then turned into a gas
• First Ionisation Energy

  The energy required to remove 1 mole of electrons from 1 moles of gaseous atoms to form 1 mole of gaseous 1+ ions

  E.g. O(g) ---> O+ + e-
• Ion Detection

  Fourth stage of TOF spectrometry

  The negatively charged plate detects charged particles and a mass spectrum is produced
• Ion Drift

  Third stage of TOF spectrometry

  The ions enter a region with no electric field, so they drift through it

  The lighter the ion, the faster they will drift
• Ionisation


  First stage of TOF spectrometry

  The sample can be ionised by electrospray ionisation or electron impact ionisation
• Isotope


  Atoms of the same element with the same number of protons but a different number of neutrons
• Nuclear Charge


  Total charge of all the protons in the nucleus

  It has the same value as the atomic number (increases as you go across the periodic table)
• Second Ionisation Energy


  The energy required to remove 1 mole of electrons from 1 moles of gaseous 1+ ions to form 1 moles of gaseous 2+ ions

  E.g. O-(g) ---> O2+(g) + e-
• Atom Economy


  The measure of the amount of starting materials that end up as useful products

  Percentage atom economy = Molecular mass of desired product/ Sum of molecular masses of all reactants X100
• Limiting Reagent


  The reaction that is completely used up since it limits the amount of products formed
• Percentage by Mass


  A value representing the concentration of an element in a compound or a component in a mixture

  Percentage by mass = Mass of desired component/ Total mass of the mixture X100
• Percentage Yield


  The percentage ratio of the actual yield of product from a reaction compared with the theoretical yield

  Percentage yield = Actual yield/ Theoretical Yield X100
• Relative Atomic Mass


  The average mass of an atom of an element compared to 1/12th the mass of an atom of carbon-12
• Relative Molecular Mass


  The average mass of one molecule of an element or compound compared to 1/12th the mass of an atom of carbon-12
• Co-ordinate Bond


  A coordinate (dative covalent) bond contains a shared pair of electrons with both electrons supplied by one atom
• Covalent Bond


  A shared pair of electrons between two non-metals
• Electronegativity


  The power of an atom to attract an electron pair in a covalent bond
• Electrostatic Forces


  The strong forces of attraction between oppositely charged ions
• Hydrogen Bonding


  An interaction between a hydrogen atom and and electronegative atom, (commonly nitrogen, fluorine or oxygen)

  The slightly positive hydrogen is attracted to the lone pair on the electronegative atom

  Hydrogen bonds are stronger than VDW and dipole-dipole but weaker than ionic and covalent bonds
• Intermolecular Forces


  The forces which exist between molecules

  The strength of the intermolecular forces impact physical properties like melting/boiling point
• Ionic Bond


  A metal atom loses electrons to form a positively charged ion and a non-metal atom gains these electrons to form a negatively charged ion

  An ionic bond is formed between the oppositely charged ions
• Permanent dipole-dipole forces


  When molecules with polar covalent bonds interact with dipoles in other molecules dipole-dipole intermolecular forces are produced between the molecules

  These intermolecular forces are generally stronger than VDW forces but weaker than hydrogen bonding
• Polar Bond


  A covalent bond between two atoms in which the electrons in the bond are unevenly distributed

  This causes a slight charge difference, including a dipole in the molecule
• Calorimetry


  The process of measuring the amount of energy absorbed or released during a chemical reaction
• Endothermic Reaction


  An endothermic reaction is one that takes in energy from the surroundings so the temperature of the surroundings decreases

  In an endothermic reaction, the energy needed to break existing bonds is greater than the energy released from forming new bonds