1. L.O. To be able to describe metallic bonding. To be able to explain the properties of materials with metallic bonding. Metallic Bonding

2. IONIC BONDING COVALENT BONDING METALLIC BONDING SOLIDS Some conduct electricity only when MOLTEN Some DO NOT conduct electricity even when molten Some conduct electricity when solid or molten eg NaCl, MgO, CaF 2 eg Diamond, P 4, SiO 2, I 2, S 8 eg Na, Mg, Al, Cu, Zn, Hg GASES LIQUIDS ALWAYS SIMPLE, COVALENTLY BONDED MOLECULES eg Br 2, H 2 Oeg N 2, O 2, CO

3. These cations are arranged in a giant lattice structure The outer electrons are free to move around the cation lattice. This is known as a sea of delocalised electrons. Metallic Bonding model says : Metal atoms are detached from ALL of their outer energy level electrons to form cations (+ve ions) Metallic Bonding

4. net attraction between cations + and delocalised outer electrons e - Metallic bonding = Cations (+) in 3D lattice Mobile sea of delocalised electrons + ++ + + + + ++ + + + + ++ + + + + ++ + + + e-

5. 1. High conductivity properties of metals – electricity & heat 2. Malleability of metals – can bend and beat into shape

6. How does this model explain typical metal properties? 1.Very good conductors of electricity and heat - in solid or liquid state - electricity or heat energy carried by EASILY mobile delocalised electrons Conductivity increases from Na to Mg to Al because +- Electrons move  +ve electrode Heavy cations remain fixed e e e e e e e e e e e - flow causes electric current 1, 2 and 3 delocalised electrons per atom respectively

7. 2.Malleability - can beat and bend into shape WITHOUT breaking metallic bonds This means the layers of cations “slide” over each other, still bonded by delocalised electrons Sliding can occur in all dimensions

8. 3.Melting Point Trend Down Groups? This is because there are same number of delocalised electrons per atom, but cations (1+) HEAVIER and LARGER LiNaKRbCs 454371336312302/ K Therefore LESS STRONGLY held in place by attraction of fixed number of delocalised electrons. DOWN metal groups (eg grp 1), melting points DECREASE

9. Across periods, melting points of metals increase because the number of delocalised electrons per atom increases ( 1  2  3 ), and the charge on cations increases ( 1+  2+  3+ ) Therefore MORE STRONGLY held in place by increasing force of attraction. NaMgAl 371922933/ K Also, conductivity will increase Na  Mg  Al as number of delocalised e- INCREASES 4.Melting Point Trend Across Periods?

10. Make sure you have notes defining the following terms: close-packing delocalised electrons metallic bonding Complete the Activity on p67 Due: Tuesday 12 th Oct