Redox Reactions

• What happens to an atom when it gains electrons?


  It becomes more negative.
• What happens to an atom when it loses electrons?


  It becomes more positive.
• What is oxidation in terms of electron transfer?


  Oxidation is the loss of electrons from an atom.
• What is reduction in terms of electron transfer?


  Reduction is the gain of electrons by an atom.
• What occurs in a redox reaction?


  • One element or compound gains electrons (reduction).
  • Another element or compound loses electrons (oxidation).
  • Both processes occur simultaneously.
• What are the reactants in a chemical reaction responsible for?


  They either lose or gain electrons.
• What is the reducing agent in a chemical reaction?


  The reactant that undergoes reduction.
• What is the oxidizing agent in a chemical reaction?


  The reactant that undergoes oxidation.
• Can oxidation occur without reduction?


  No, oxidation cannot occur without reduction.
• What are oxidation-reduction reactions commonly called?

  REDOX reactions.
• What is the definition of oxidation in terms of a molecule, atom, or ion?


  Oxidation is the loss of electrons by a molecule, atom, or ion.
• What is the term for the reactant that loses electrons in a reaction?


  Reducing agent/Reductant.
• Why is the reactant that loses electrons called a reducing agent?


  Because it is oxidized.
• What is the oxidation number of any uncombined element?

  Zero
• Do many atoms or ions have fixed oxidation numbers in compounds?


  Yes
• What is the oxidation number of an element in a monoatomic ion?


  It is always the same as the charge
• What is the sum of the oxidation numbers in a compound?


  It is zero
• What is the sum of the oxidation numbers in an ion?


  It is equal to the charge on the ion
• In a compound or an ion, which element is given the more electronegative oxidation number?


  The more electronegative element
• What are the fixed oxidation numbers for Group 1 and Group 2 elements?


  • Group 1 elements: +1
  • Group 2 elements: +2
• What is the oxidation number of fluorine?


  • 1
• What is the oxidation number of hydrogen, except in hydrides?


  +1
• What is the oxidation number of oxygen, except in peroxides?


  • 2
• What is the oxidation number of oxygen in peroxides?


  • 1
• What is the definition of the oxidation number of an element?

  It is the charge that an atom would have in a compound if all the bonds were ionic
• What are the rules for assigning oxidation numbers?

  • All elements including diatomic molecules have an oxidation number of zero
  • Group 1 ions: +1, Group 2 ions: +2, Group 17 ions: -1
  • Hydrogen: +1 (except in hydrides: -1)
  • Oxygen: -2 (except in peroxides: -1)
  • Compounds (as they are neutral ) have a net oxidation number of 0
  • Polyatomic ions have a net oxidation number equal to its charge