Bonding

1. Ion Shared pair of electrons Molecule Bonding What do you know about bonding? Intermolecular forces Electrostatic forces

2. Learning Objectives • Define Key terms. • Describe Ionic Bonding • Construct Dot/Cross diagrams for ionic compounds.

3. Match up Now look in your book for a copy of the ‘definition’ what do you think the key parts are??

4. Ionic Bonds • Electrons are transferred from the metal atom to the non metal atom. • Oppositely charged ions are formed which are held together by electrostatic attraction. • A giant ionic lattice is formed.

5. THE IONIC BOND Ionic bonds tend to be formed between elements whose atoms need to “lose” electrons to gain the nearest noble gas electronic configuration (n.g.e.c.) and those which need to gain electrons. The electrons are transferred from one atom to the other. Sodium Chloride Na 1s2 2s2 2p6 3s1 Na+ 1s2 2s2 2p6 Cl 1s2 2s2 2p6 3s2 3p5Cl¯1s2 2s2 2p6 3s2 3p6 An electron is transferred from the 3s orbital of sodium to the 3p orbital of chlorine; both species end up with the electronic configuration of the nearest noble gas theresulting ions are held together in a crystal lattice by electrostatic attraction. _ +

6. Half equations and electron configurations Na ——> Na+ + e¯ 1s2 2s2 2p6 3s1 1s2 2s2 2p6 Cl + e¯ ——> Cl¯ 1s2 2s2 2p6 3s2 3p5 1s2 2s2 2p6 3s2 3p6

7. THE IONIC BOND FORMATION OF MAGNESIUM CHLORIDE e¯ Cl ELECTRON TRANSFER Mg Cl e¯ Mg ——> Mg2+ + 2e¯ and 2Cl + 2e¯ ——> 2 Cl¯ What would the electron configurations be? For all species? (4 of them) Draw your own diagrams with electron configurations and half equations for: Calcium oxide (CaO), Sodium Oxide (Na2O) and Aluminium Fluoride (AlF3)

8. This question is about different models of bonding and molecular shapes. Magnesium sulfide shows ionic bonding. (i) What is meant by the term ionic bonding? ......................................................................................................................... ......................................................................................................................... [1] (ii) Draw a ‘dot-and-cross’ diagram to show the bonding in magnesium sulfide. Show outer electron shells only.

9. Ionic bonding and the periodic table • 1. Drawn a dot/cross diagram (outer shell) for a) MgO, b) CaBr2, c) Na3P, d) Al2O3 • 2. Write out the electron configuration for K and K+, S and S2-

10. Learning Objectives • State common molecular ions • Be able to predict ionic charge • Apply to exam questions

11. Notes • In general: • Group 1-3 lose elctrons to form the configuartion of PREVIOUS noble gas. • Group 5-7 gain electrons to form the configuration of the NEXT noble gas. • Be, C, B and Si don’t tend to form ions due to too much energy being required to remove electrons. • Transistion Metals: • Iron (II) Fe 2+ Iron (III) Fe 3+ • Copper (I) Cu+ Copper (II) Cu 2+ (Just look at the roman numerals)

12. Ions formed

13. Molecular Ions • Some such as NH4+ andOH- can be worked out. • Others such as sulphate, think about what the acid would be.

14. Working out ionic formulae

15. Questions

16. Apply to exam question