Chemistry ES

• Atom economy


  In industrial chemical processes, it is desirable to have a high atom economy for a reaction. This means there is little or no waste product, only the desired product. This means the process is more economically viable for industrial-scale manufacturing. It also helps to preserve raw materials.
• Electrons


  Contained within orbitals. These orbitals correspond with blocks on the Periodic Table. Each element in the block has outer electrons in that orbital.
• Blocks of the periodic table

  • Group 1 metals
  • Group 2 metals
  • Group 7 elements
• Group 1 metals


  Lose an electron to form 1+ ions
• Group 2 metals


  Lose two electrons to form 2+ ions
• Group 7 elements


  Gain an electron to form 1- ions. They are known as the halogens and their negative ions are known as halide ions.
• Redox reaction

  A reaction in which oxidation and reduction take place. Oxidation is the loss of electrons, or increase in oxidation number. Reduction is the gain of electrons, or decrease in oxidation number.
• OILRIG


  Oxidation Is Loss, Reduction Is Gain (mnemonic for remembering redox rule)
• Disproportionation


  When a species is simultaneously reduced and oxidised to give two different products.
• Rules for assigning oxidation numbers

  • The oxidation number of an element is zero
  • In neutral compounds, the sum of the oxidation states of all the atoms is 0
  • Oxidation numbers in a charged compound add up to the total charge
  • More electronegative elements in a substance have a negative oxidation state while less electronegative elements have a positive oxidation state
  • Hydrogen has an oxidation number of +1
  • Oxygen has an oxidation number of -2
  • Halogens have an oxidation number of -1
  • Group I metals have an oxidation number of +1
  • Group II metals have an oxidation number of +2
• Oxygen has an oxidation number of -1 in peroxides. Hydrogen has an oxidation number of -1 in metal hydrides.
• Roman numerals


  Used to give the oxidation number of an element that has a variable oxidation state, depending on the compound it's in.
• Examples of using Roman numerals

  • Copper (II) sulphate - copper has an oxidation number of +2

  Iron (II) sulphate (VI) - iron has an oxidation number of +2, sulfur has an oxidation number of +6
• Oxidising agent

  Accepts electrons from the species that is being oxidised. Therefore, it gains electrons and is reduced.
• Reducing agent


  Donates electrons to the species being reduced. Therefore, it loses electrons and is oxidised.
• Electrolysis


  The decomposition of a molten or aqueous ionic compound (an electrolyte) by passing an electric current through it. The solution must contain a cathode (negative electrode) and an anode (positive electrode).
• Electrolysis of molten ionic compounds

  Cations move to the cathode and gain electrons to form atoms

  Anions move to the anode and lose electrons to form atoms