Oxidation and Reduction

Little set of cards reviewing the rules for giving oxidation numbers

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  • Created by: Maddison
  • Created on: 02-06-09 09:54

What is REDOX?

REDOX reactions are reactions in which both OXIDATION and REDUCTION occur

OXIDATION is the LOSS of electrons from a species

REDUCTION is the GAIN of electrons to a species

Oxidation and Reduction can also be thought of in terms of the loss and gain of hydrogen and oxygen...

Oxidation is thegain of oxygen or the loss of hydrogen
Reduction is thegain of hydrogen or the loss of oxygen

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Oxidation Number [State]

"Oxidation numbers are the number of electrons that atoms lose, gain or share when they form bonds with other elements"

ON (Oxidation Numbers) can be +ve, -ve or 0

OXIDATION shows an INCREASE in oxidation number -- it becomes more +ve

REDUCTION shows a DECREASE in oxidation number -- it becomes more -ve

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Assigning Oxidation Numbers - Rules Part I

  • ON of an atom in a free element is 0

  • Thetotal ON of all the atoms in a compound is 0

  • The ON of monatomic (single atomed) ions is the same as the charge on the ion
  • In a polyatomic ion (many atomed), the total ON is equal to the charge on the molecule/ion.
  • In covalent compounds, the more electronegative element has the-ve ON
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Assigning Oxidation Numbers - Rules Part II

In compounds...

  • Group One metals have an ON of +1
  • Group Two metals have an ON of+2
  • Hydrogen has an ON of +1
  • Fluorine has an ON of -1
  • Oxygen has an ON of -2

In metallic compounds...

  • Group 7 elements (Cl, Br, I) have an ON of -1
  • Group 6 elements ( O, S ) have an ON of -2
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Bits and Bobs to bear in mind...

  • Metals generally lose electrons to form +ve ions
  • Non metals usually react by gaining electrons to form negative ions, and thus have a decrease in ON
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