1. Ions & formation of Ionic compounds
A ‘type of’ chemical reaction you need to master…
IONS: an atom or molecule with a net electric charge due to the loss or gain of one or more electrons, eg Mg2+

2. Unlike charges attract
Side point:
Electrostatic Forces
Unlike charges attract
Like charges repel…

4. Atom has extra electrons I.e. wants to get rid of them
Fe2+ or Fe3+
+ve
CATION
Atom has extra electrons
I.e. wants to get rid of them
NH4+
Ca2+
metals (Mg) lose electrons ---> cations
sodium
hydrogen
Na+ H+

5. -ve F-
CO32-
ANION
Atom needs electrons
i.e. wants to grab them
OH-
SO42-
nonmetals (F) gain electrons ---> anions
chlorine
O2-
oxygen
Cl-

6. CATION
+ve
How to remember?
Cation has a t

8. Review
State the number of protons, neutrons, and electrons in each of these ions.
39 K O Ca +2
#p+ ______ ______ _______
#no ______ ______ _______
#e- ______ ______ _______

9. Naming ions & ionic compounds
Names of cations are the same as the names of the elements.
Na+ = sodium ion
Names of anions = Name of element but ending with “-ide”

10. Learning Check Complete the names of the following ions. Ba2+ Al3+ K+
_________ __________ _________
N3 O2 F
_________ __________ _________
P3 S2 Cl

11. Solution Ba2+ Al3+ K+ barium aluminum potassium N3 O2 F
nitride oxide fluoride
P3 S2 Cl
phosphide sulfide chloride

12. When an atom loses or gains electrons it becomes Ion.

13. Ions combine together to form a compound so that there is no excess charge

14. Ionic bonding (metal + non-metal)
Look!
Group 7 element
Look!
Group 1 element
Very strong forces of attraction between positive and negative ions = ionic bond

15. Mg + O = MgO
Metal gas Metal oxide
2Mg + O MgO
Heat
Mg O2-
Ions ?

16. Mg (2,8,2) → Mg2+ (2,8) magnesium ion
Electron arrangement for Mg (2,8,2)
Mg has two valence electrons.
(Valence electrons are…
Atoms are stable when their
outer shell is full
An atom may lose or gain 1,2 or 3
electrons to form an ion.
An ion is an atom or compound that
has lost or gained electrons
Mg (2,8,2) → Mg2+ (2,8) magnesium ion
Mg 2 electrons get ‘lost’ in a Chemical reaction to another substance!
Compare with O (2,6) → O2- (2,8) Oxygen ion
Here O ‘gains’ 2 electrons in a Chemical reaction to another substance!

17. The formula is Al2O3 Aluminium Oxide Aluminium Oxygen
To work out the number of ions of each element we need to balance the number of electrons being given and taken.
2 x 3= 6 electrons from the aluminium and
3 x 2 = 6 electrons to the oxygen 2- 3+ 2- 3+ 2-
The formula is Al2O3
Aluminium Oxide

18. Polyatomic ions are made up of more than one element
OH- = hydroxide ion
NO3- = nitrate ion
NH4+ = ammonium ion
CO32- = carbonate ion
SO42- = sulfate ion
PO43- = phosphate ion
HCO3- = hydrogen carbonate ion
Fiddly naming rule – learn in senior Chemistry!
Since transition metals and poor metals can form ions of more than one charge, the name of the cation has to include the charge:

20. Examples of Ionic Compounds with Two Elements
Formula Ions Name
cation anion
NaCl Na+ Cl- sodium chloride
K2S K S2- potassium sulfide
MgO Mg2+ O2- magnesium oxide
CaI2 Ca2+ I- calcium iodide
Al2O3 Al O2- aluminum oxide

21. Learning Check Write the names of the following compounds.
1) CaO ___________
2) KBr ___________
3) Al2O3 ___________
4) MgCl2 ___________

22. Solution Write the names of the following compounds:
1) CaO calcium oxide
2) KBr potassium bromide
3) Al2O3 aluminum oxide
4) MgCl2 magnesium chloride

24. http://science. nayland. school

25. Learning Check Select the correct name for each. A. Fe2S3
1) iron sulfide
2) iron(II) sulfide
3) iron(III) sulfide
B. CuO
1) copper oxide
2) copper(I) oxide
3) copper(II) oxide

26. Solution Select the correct name for each. A. Fe2S3
3) iron (III) sulfide Fe3+ S2-
B. CuO
3) copper (II) oxide Cu2+ O2-

27. One Last Learning Check
Write the nuclear symbol form for the following atoms or ions:
A. 8 p+, 8 n, 8 e- ___________
B. 17p+, 20n, 17e- ___________
C. 47p+, 60 n, 46 e- ___________