Woodhouse Chemistry
Ions, Formulae and Equations
1. Relationship between the charges on simple ions and their position in the Periodic
Table
2. Understanding a Charge Table
See attached
3. Writing formulae using ions
To write the formula of a compound the charges on the ions must cancel out.
Using the ‘Charge table’, you can turn the name of a compound into its formula.
Name of compound
Sodium chloride
Ions
Balance charges
Iron (III) oxide
Lithium sulphate (VI)
Exercise 1: Work out the formulae of the following simple compounds.
a
b
c
d
e
f
Sodium fluoride
Lithium iodide
Magnesium sulfide
Calcium oxide
Aluminium nitride
Iron (III) phosphide
g
h
i
j
k
l
Magnesium chloride
Sodium sulfide
Aluminium iodide
Lithium nitride
Magnesium nitride
Aluminium oxide
Formula
Exercise 2: Work out the formulae of the following compounds which contain polyatomic ions.
a
b
c
d
e
f
Potassium nitrate
Sodium hydroxide
Magnesium sulfate (VI)
Calcium carbonate
Aluminium phosphate
Ammonium chloride
g
h
i
j
k
l.
Iron(II) sulfate (VI)
Hydrogen chloride
Silver nitrate
Sodium hydrogencarbonate
Lead (II) carbonate
Ammonium hydroxide
Exercise 3: In this exercise you may need to use brackets in the formulae. We use brackets around
polyatomic ions whenever we need two or more of them.
e.g. sodium hydroxide, NaOH
copper hydroxide, Cu(OH)2
aluminium hydroxide, Al(OH)3
a
b
c
d
e
f
Copper (II) nitrate
Sodium sulfate (VI)
Calcium hydroxide
Sodium hydrogensulfate
Aluminium nitrate
Potassium hydrogen phosphate
g
h
i
j
k
l
Iron (III) sulfate (VI)
Copper (II) ethanoate
Ammonium carbonate
Calcium phosphate
Iron (III) carbonate
Ammonium sulfate (IV)
4. Balancing some simple equations
Write the word equation and the write in the formulae underneath it:
Sodium hydroxide + hydrochloric acid  sodium chloride + water
NaOH
+
HCl

NaCl
+ H 2O
In a balanced equation there will be the same number of atoms of each element on both sides of the arrow.
In this example there is one sodium atom in the sodium hydroxide and one in the sodium chloride. There is
one atom of hydrogen on each side also. Count the hydrogens and the chlorine.
Exercise 4
I.
Calcium carbonate  calcium oxide + carbon dioxide
II.
Hydrochloric acid + sodium hydroxide sodium chloride + water
III.
Magnesium + sulfuric acid  magnesium sulfate (VI) + hydrogen gas
IV.
Copper sulfate (VI) + zinc  zinc sulfate (VI) + copper
V.
Iron (II) oxide + calcium  calcium oxide + iron
5. More difficult equations:



you need to multiply some of the formulae to
balance the elements
Start with what changes……. there are 2 O’s in
O2 and only one in CuO. To balance it you need
2 O’s in the products. Don’t be tempted to
write CuO2, you have found the formula and
you can’t change it. Instead double the CuO
Now you have balanced the oxygen, you have 2
O’s in O2 and in the 2CuO
But you now have 2Cu’s in the products but
only one in the reactants, so double the Cu
Copper + oxygen gas  copper oxide
Cu
+
Cu
+
2Cu
2. Aluminium + oxygen gas  aluminium oxide
3. Zinc + hydrochloric acid  zinc chloride + hydrogen gas
4. Copper oxide + nitric acid  copper nitrate + water

O2
+
O2
CuO
2CuO

2CuO
Quickly double check each element, all
done!
Exercise 5: Try these harder ones (Remember…. hydrogen gas is H2, oxygen gas is O2)
1. Magnesium + oxygen gas  magnesium oxide

O2
5. Calcium carbonate + hydrochloric acid  calcium chloride + water + carbon dioxide gas
6. Sodium + oxygen gas  sodium oxide
7. Sodium hydroxide + sulfuric acid  sodium sulfate + water
8. Sodium + water  sodium hydroxide + hydrogen gas
9. Aluminium + Iron (III) oxide  aluminium oxide + iron
10. Magnesium nitrate  magnesium oxide + oxygen gas + nitrogen dioxide (NO2)
The last one is difficult, if you can’t balance it first time through, try starting with two magnesium nitrates.
To prepare for September
 Enjoy yourself and relax 
 Learn the ‘Charge Table’ off by heart! (we will be
testing you on this)
 Have a go at balancing the equations in exercises 4 & 5
 Read up on ‘Atomic structure’ which is the first topic
we will be studying. (AQA Chemistry A level)
1+
Lithium
Sodium
Potassium
Rubidium
Caesium
Silver
Hydrogen
Copper (I)
2+
+
Li
Na+
K+
Rb+
Cs+
Ag+
H+
Cu+
3+
Beryllium
Magnesium
Calcium
Strontium
Barium
Copper (II)
Iron (II)
Lead
Zinc
2+
Be
Mg2+
Ca2+
Sr2+
Ba2+
Cu2+
Fe2+
Pb2+
Zn2+
Boron
Aluminium
Gallium
Iron (III)
33+
B
Al3+
Ga3+
Fe3+
Nitride
Phosphide
23-
N
P3-
Oxide
Sulfide
Selenide
12-
O
S2Se2-
Fluoride
Chloride
Bromide
Iodide
Hydride
FClBrIH-
Simple ions
Polyatomic ions
1+
3-
Ammonium
NH4+
Hydronium/oxonium
H3O+ Phosphate (III)
/ phosphite
Phosphate (V)
2PO43-
Carbonate
PO33- Sulphate (VI)
1CO32SO42-
Sulphate (IV) /
Sulphite
Chromate (VI)
SO32-
Dichromate
(VI)
Ethandioate
Cr2O72-
CrO42-
C2O42-
Hydrogen
carbonate
Hydrogen
sulphate
Nitrate (V)
HCO3-
Nitrate (III) /
Nitrite
Hydroxide
NO2-
Manganate
(VII)
Ethanoate
MnO4-
HSO4NO3-
OH-
CH3COO-