WK09

• Hydrogen atoms usually have an oxidation number of +1.
• Atoms of Group 7 elements usually have an oxidation number of -1.
• Atoms of Group 1 elements always have an oxidation number of +1.
• Atoms of Group 2 elements always have an oxidation number of +2.
• Atoms of Group 3 metals have an oxidation number of +3.
• Oxygen atoms usually have an oxidation number of -2.
• The sum of oxidation numbers in neutral compounds is 0.
• Atoms in all elements always have an oxidation number of 0.
• The sum of oxidation numbers in ions is equal to the overall charge.
• Atoms with variable oxidation numbers use Roman numerals to represent the corresponding positive oxidation number e.g. (II) = +2 and (IV) = +4.
• When Roman numerals are used the numeral will be added to the name e.g. Iron (III) oxide.