Unit 1.1

• An ammonium ion is NH4 charge +1
• A Hydrogen carbonate ion us HCO3 with a -1 charge
• A hydroxide ion is OH with a -1 charge
• A nitrate ion is NO3 with a -1 charge
• A carbonate ion is CO3 with a -2 charge
• A sulphate ion is SO4 with a -2 charge
• A phosphate ion is PO4 with a -3 charge
• The oxidation number is the number of electrons that need to be added or lost from an element to make it neutral. For example, the iron ion is Fe with a +2 charge. An iron ion needs 2 electrons to make it neutral, so it's oxidation number is +2.
• The oxidation number of an uncombined element is zero.
• The sum of the oxidation numbers in a compound is the overall charge.
• In compounds, the oxidation number of group 1 metals are +1 and group 2 metals are +2
• The oxidation number of oxygen is -2 in compounds except with fluorine or in peroxides.
• The oxidation number of hydrogen is +1 in compounds except in metal hydrides (like NaH)
• In chemical species with atoms of more than one element, the most electronegative element is given the negative oxidation number.