1. Starter Question What is the shape of the following compounds BF 3 OCl 2 NH 4 + What type of bonding occurs in the following compounds Barium Chloride Silicon carbide Dinitrogen tetroxide Trigonal planar angular tetrahedral ionic covalent What is a prefix? Something that is placed infront of a word. In Chemistry it usually tells us the size of a unit or number of atoms Do not hand in homework until you have completed the starter question. You will need it to help you

2. Number of electron pairs Number of bonded electron pairs Number of non- bonding or lone pairs Shape 330 Trigonal planar 440Tetrahedral 431Pyramidal 422Angular 413Linear 550Trigonal bipyramidal

3. Nomenclature Sometimes the name of a compound tells us what its formula is. To work out the formula we need to look for a few things 1. Prefixes PrefixMeaning Mono Di Tri tetra 1 2 3 4

4. When prefixes are used in naming a compound they determine what the formula is and not any other method Using this information can you determine the formula of the following compounds? Carbon monoxide Sulphur dioxide Diphosphorus pentoxide Carbon tertrahydride CO SO 2 P2O5P2O5 CH 4

5. 2. Endings The ending of a compound can tell us which elements are present. ide- ite- ate- This means that only the lements in the name are present in the compound These means that there is a hidden oxygen in the compound

6. Using this information name the following elements in the following compounds Sodium chloride Carbon tetrahydride Copper sulphate Sodium hydrogen carbonate Sodium chlorine Carbon hydrogen Copper sulphur oxygen Sodium hydrogen carbon oxygen

7. 3. Valencies The valency of an element can be used to determine the formula Remember the valency of an element is different from the number of valence electrons 1 2 1 0 2343

8. The cross- over method for determining formula 1. Write out the symbol of the elements involved in the formula Aluminium oxide AlO 2. Write the valency of each element below it AlO 32 3. Cross over the valencies AlO 32 23

9. 4. If the number have a common denominator divide down e.g. CO 42 24÷2 12 5. Write out the formula Al 2 O 3 NB: Remember to use subscripts to show how many of each atom is present in the formula

10. Now try to determine the formula of the following compounds Magnesium oxidecalcium sulphide Calcium nitridepotassium oxide

11. Now complete the worksheets you have been handed. When complete they need to be handed in. When finished please complete questions p221- 226 in the textbook