Chemistry AS level - Introduction to Ionic formulae

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