1. Ionic Bonding

2. Today’s objectives In today’s class you should learn about
What an ion is ( a cation and an anion)
What an ionic bond is
How ionic bonds are made in some simple compounds
How to draw dot and cross diagrams
To investigate the characterisitics of ionic compounds

3. How can reactive metal atoms become stable positive ions?

4. Definition

5. Sodium + Chlorine  Sodium Chloride- +
Chlorine, Cl
Sodium, Na
Each sodium atom transfers one electron to each chlorine atom and an ionic electrostatic bond is formed

7. Formation of an ionic bond

8. Ionic lattices + - - + - - - + + + - + + - - - - + + + - - - + + + - -
In an ionic compound, millions and millions of ions are packed together in a regular cubic arrangement, joined by ionic bonds. This forms a giant 3D structure called an ionic lattice. + - - + - - - + + + - + + - - - - + + + - - - + + + - - - + + + - - - + + +

9. The crystal structure of sodium chloride

10. These are crystals of sodium chloride
Acknowledgement
The image is a coloured scanning electron micrograph (SEM) of  common salt,  sodium chloride,  recrystallised from distilled water.  The salt crystal  is  built up  from  a cubic  lattice  of sodium and chloride ions.  In the  absence  of  impurities  the  exact cubic  crystal form is  produced.  This micrograph shows that in practice this basic cube is  usually disrupted  by  dislocations;   these  give rise to crystals with a variety of shapes,  although  they all    retain    the    basic    cubic   symmetry. Magnification: x280 at 5x7cm size. x975 at 10x8‘.
Credit: Andrew Syred/Science Photo Library
These are crystals of sodium chloride
All ionic compounds form lattices and crystals when solid.

11. Calcium + Oxygen  Calcium Oxide2+ 2-
Oxygen, O
Calcium, Ca
Each calcium atom transfers two electrons to each oxygen atom and an ionic electrostatic bond is formed

12. Formation of an ionic bond

13. Calcium Oxide – A Regular Lattice

14. Dot and Cross Diagrams Sodium Chloride & Calcium Oxide- + X X X X Na + Cl X Na Cl X X X X X X X X X 2+ 2- X X X X Ca + O Ca X O X X X X X X X

15. The Characteristics of Ionic Compounds
They are composed of ions which form a rigid structure (lattice)
They are brittle
They have high melting points and high boiling points
When dissolved in solution or when melted they conduct electricity.
They are usually soluble in water

16. Ionic compounds are brittle – they shatter when they are hit.
force + - + - + -
repulsion + -
When the lattice is hit, a layer of ions is shifted so that ions with the same charges are lined up together.
These like charges repel each other, thereby splitting the lattice.

17. High Melting and boiling points
Ionic substances generally have high melting and boiling points
because
all the atoms are strongly bonded together to form a continuous 3D lattice.
A large amount of energy is needed to break these bonds. + -
strong ionic bonds holds ions together

18. How do properties differ?

19. Bonding and electrical conductivity

20. Conductivity – ionic substances
Ionic substances cannot conduct electricity when solid because the ions are bonded together in the lattice. + -
ions cannot move to carry a charge
When liquid (molten) or dissolved, however, the ions are able to break free of the lattice. + -
ions are able to move and carry a charge

21. Solubility
Many ionic substances dissolve in water because water molecules have a slight electrical charge and can attract the ions away from the lattice. + -

22. Solubility experiment
Points to note are that:
when a solute dissolves, mass is conserved.
when a solute dissolves, the solute and solvent particles intermingle.
increasing the temperature increases the rate of dissolving.

23. Ionic Materials in Everyday Life
Farmers add lime (calcium oxide) to soil to reduce the acidity of the soil
Athletes take salt tablets to replace salt lost through sweating

24. Mandatory Experiment
The Tests for Anions

25. Test for Chloride (Cl-) ions
Add silver nitrate solution.
A white precipitate is produced
This white precipitate is soluble in ammonia solution

26. Test for Chloride (Cl-) ions

27. Test for nitrate (NO3-) ions
Add cold iron(II) sulfate solution.
Then add concentrated sulfuric acid down the sides of the test tube
A brown ring forms.

28. Test for carbonate (CO32-) & hydrogencarbonate (HCO3-) ions
Add dilute hydrochloric acid solution.
Carbon dioxide gas is released which turns limewater milky
Add magnesium sulfate solution to a fresh sample
The carbonate produces a white precipitate. The hydrogencarbonate does not.

29. Test for sulfite (SO32-) and sulfate (SO42-) ions
Add barium chloride solution.
A white precipitate is produced
Add hydrochloric acid solution
The white precipitate dissolves  Sulfite
The white precipitate remains  Sulfate

30. Tonight’ s homework Write up today’s experiments
From the worksheet question 60
Learn all of the anion tests done so far off by heart