When metals react with non-metals, electrons are transferred from the metal atoms to the non-metal atoms. This results in the metal atoms becoming positively charged ions with fewer electrons than protons and the non-metal atoms becoming negatively charged ions with more electrons than protons. Examples of common ionic charges are provided for elements in different groups of the periodic table. The document also explains how to write chemical formulas for ionic compounds by writing the symbols for the cation and anion.

1. Ionic Formulae
When metals combine with non-metals they do not share
electrons. Electron(s) are transferred from the metal
atom(s) to the non-metal atoms.
This results
in
Metal atoms with fewer
electrons than
protons.These are called
positive ions.
Non-metal atoms with
more electrons than
protons. These are
called negative ions.

2. Element E/a Ion E/a
Sodium 2,8,1 Na+
2,8
Calcium 2,8,8,2 Ca2+
2,8,8
Aluminiu
m
2,8,3 Al3+
2,8
Chlorine 2,8,7 Cl-
2,8,8
Oxygen 2,6 O2-
2,8
Nitrogen 2,5 N3-
2,8
Some examples

3. Group 1
+1
Group 2
+2
Group 3
+3
Group 5
-3
Group 6
-2
Group 7
-1
Ion Charges
Transition Metals - Charge is
the same as the valency
(Roman number) and all are
positive ions.
Group ions e.g. nitrate
(NO3
-) - The charge is given
in the table in the data
book.

4. Writing Ionic Formulae
Sodium chloride Na+
Cl-
Calcium carbonate Ca2+
CO3
2-
Copper(II) nitride (Cu2+
)3(N3-
)2
Ammonium sulphate (NH4
+
)2SO4
2-

5. TRY…
Aluminium fluoride Al3+
(F-
)3
Tin(II) sulphide Sn2+
S2-
Lithium oxide (Li+
)2O2-
Ammonium phosphate (NH4
+
)3PO4
3-
Iron(III) chromate (Fe3+
)2(CrO4
2-
)3

6. TRY…
Aluminium fluoride Al3+
(F-
)3
Tin(II) sulphide Sn2+
S2-
Lithium oxide (Li+
)2O2-
Ammonium phosphate (NH4
+
)3PO4
3-
Iron(III) chromate (Fe3+
)2(CrO4
2-
)3