The oxidation number of an element is the “charge” the element would have if all of its bonds were completely ionic; that is, if the electron pairs of each bond were transferred to the more electronegative atom.

For monatomic ions the oxidation number is simply the charge of the ion. For covalently bonded elements the oxidation number is a bookkeeping device and does not mean that the element carries an actual charge.

Determine the oxidation state for each of the elements below.

The oxidation state of sulfur in sulfurous acid H2SO3 is ___

• -7
• -6
• -5
• -4
• -3
• -2
• -1
• 0
• +1
• +2
• +3
• +4
• +5
• +6
• +7

The oxidation state of iodine in iodine heptafluoride IF7 is ___

• -7
• -6
• -5
• -4
• -3
• -2
• -1
• 0
• +1
• +2
• +3
• +4
• +5
• +6
• +7

The oxidation state of arsenic in arsenious acid H3AsO3 is ___

• -7
• -6
• -5
• -4
• -3
• -2
• -1
• 0
• +1
• +2
• +3
• +4
• +5
• +6
• +7