Oxidation number

• What is the oxidation number of uncombined elements like Ne?

  0
• What is the oxidation number of atoms in molecules bonded to identical atoms, such as O2?

  0
• How is the oxidation number of a monatomic ion determined?

  It equals the ion's charge
• What is the oxidation number of Fe in Fe3+?

  +3
• What is the sum of oxidation numbers in a molecular ion?

  It equals the overall charge
• In the sulfate ion SO42-, what are the oxidation numbers of S and O?

  S is +6 and O is -2
• What is the sum of oxidation numbers in a neutral compound?

  It is 0
• In Al2O3, what are the oxidation numbers of Al and O?

  Al is +3 and O is -2
• What is the usual oxidation number of combined oxygen?

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

  • 1
• What is the oxidation number of oxygen in OF2?

  +2
• What is the usual oxidation number of combined hydrogen?

  +1
• What is the oxidation number of hydrogen in metal hydrides?

  • 1
• How are oxidation numbers assigned in compounds or ions with two non-metals?

  • The negative oxidation number is assigned to the more electronegative element.
  • Fluorine always has an oxidation number of -1.