Redox

• The redox number of elements is always zero.
• In a pure element, any bonding is to atoms of the same element.
• Each atom in a compound has an oxidation number.
• An oxidation number has a sign ( + or - ) which comes BEFORE the number.
• The oxidation number of an ion of an element is numerically the same as the ionic charge but the sign comes before the number.
• What is the oxidation number of Oxygen?

  -2
• What is the oxidation number of Hydrogen?

  +1
• What is the oxidation number of Fluorine?

  -1
• What is the oxidation number of Hydrogen in metal hydrides?

  -1
• What is the oxidation number of Oxygen in peroxides?

  -1
• What is the oxidation number of Oxygen when bonded to Fluorine?

  -2
• Roman numerals are used in the names of compounds of elements that form ions with different charges.
• The Roman numeral shows the oxidation state/number of the element, without a sign.
• Iron (II) represents Fe2+ with oxidation number +2.
• Iron (III) represents Fe3+ with oxidation number +3.
• Oxidation is addition of oxygen.
• Reduction is removal of oxygen.
• Redox reactions involve reduction and oxidation.
• If something is reduced, something else must be oxidised.
• Reduction is the GAIN of electrons.
• Oxidation is the LOSS of electrons.
• Reduction is a decrease in oxidation number.
• Oxidation is an increase in oxidation number.
• Electronegativity is the ability of an atom to attract the bonding pair of electrons towards itself in a covalent bond.
• Oxidation number is a measure of the number of electrons that an atom uses to bond with atoms of a different element.
• Oxidising agent is a reagent which oxidises another species by accepting electrons from the other species (and itself reduced).
• Reducing agent is a reagent which reduces another species, it donates electrons to the other species (gets oxidised itself).
• A more positive value means a stronger reducing agent or weaker oxidising agent.
• Redox is a reaction in which both oxidation and reduction occurs.
• Disproportionation is a reaction in which the same element is simultaneously both oxidised and reduced.
• The sum of all oxidation numbers for each atom within a compound must equal zero.
• The oxidation states of bonded group 1 and group 2 metals are usually +1 and +2 respectively.
• The more electronegative species will have the negative value.
• Electronegativity increases across a period and decreases down a group.
• The oxidation number of sulfur in S4O62- is a fraction.
• Metal + Acid -----> Salt + Hydrogen
• What would happen to the oxidation number if an atom lost electrons?

  Increase
• What would happen to the oxidation number if an atom gained electrons? 


  Decrease
• What is the formula of chromium (III) sulfate?

  Cr2(SO4)3
• What is the oxidation number of vanadium in the ion V2O7(4-)?


  +5