2. So, what makes a bond ionic? 1. Electrons are transferred 2. Usually involves a metal (+) and non- metal (-) Opposite sides of the table 3. Products are called salts

3. Ionic compounds are tightly packed together to form ionic crystals + _ + ++ + + + + + _ _ _ _ _ _ _ _ + +++ +++ ++ _ ___ _ __ __ Positives = Negatives Strong attraction of positive to negative result in the formation of a crystal lattice Lattice fence

4. As a result, ionic compounds have a very high bond strength.

5. When determining the strength of a bond, scientist look at three things 1. Hardness 2. Melting Point 3. Boiling Point

6. Hard, Rigid, Brittle Crystalline Structure + _ + ++ + + + + + _ _ _ _ _ _ _ _ + +++ +++ ++ _ ___ _ __ __ But the structure will break in a characteristic way if a force is applied. Ionic compounds form hard crystalline structures

7. Hard, Rigid, Brittle Crystalline Structure + _ + ++ + + + + + _ _ _ _ _ _ _ _ + +++ +++ ++ _ ___ _ __ __ But the structure will break in a characteristic way if a force is applied.

8. Salt - NaCl Image from the website: http://www.soes.soton.ac.uk/resources/collection/minerals/minerals/pages/M12-Halite.htm www.csuhayward.edu/SCI/sem/back/images/salt1.gif http://www.dit.ie/DIT/science/chemistry/rsccomp/competition01/hawkesclancy/NaCl.gif

9. Melting and Boiling Points The intermolecular forces between ions are strong and require more energy to break. More Energy = Higher Temperatures Therefore, ionic compounds have _______ melting and boiling points. High

10. When ionic compounds are solid… They are nonconductors of electricity Why?  They are so tightly packed they can’t move. + _ + ++ + + _ _ _ _ _ Nothing

11. However, when they are in water (or melt)… The ions separate or dissociate, then they can move and can carry electricity. + _ + ++ + + _ _ _ _ _

12. However, when they are in water (or melt)… The ions separate or dissociate, then they can move and can carry electricity. + _ + ++ + + _ _ _ _ _ ZAP!!!

13. A special name for ionic solutions Electrolytes are ionic compounds that are dissolved in a medium. The most common medium Hint: When you hear Electrolyte, think electricity - water

14. Conductivity in Action Image from the website: http://people.bu.edu/straub/courses/demomaster/electrolytes.html Water – the mediumSugar – Covalent Bonding Table Salt – Ionic Bonding

15. Ionic Bonds are exothermic when they are made When made, they release energy Energy, usually heat, exits (exo) the system And it takes energy to break ionic bonds after they are made. This energy is called the lattice energy.

16. More about Lattice Energies The more negative the value, the harder it is to break. Lattice Energy is affected by: Size of Ions - Smaller ions are harder to pull apart. Charge of the Ion - greater positive or negative charges are harder to pull apart.

17. Size of Ions  Smaller ions have more negative values because their nuclei are closer together and they have more attraction to each other.  Therefore, it is harder to pull apart.

18. Charge of the Ion  Large positive or negative ions have a more negative lattice energy.  So they are harder to pull apart.

19. Homework Page 175: 2, 3, 4, 6 and Page 184: 26 - 29