2.  When non-metals combine together they share electrons to form molecules  A covalent bond is a shared pair of electrons Non-metal + non-metal → Covalent bonding  There are two types of covalently bonded structures:  Simple molecular (small molecules)  Macromolecular (giant structures)

3.  In some cases a large number (millions) of atoms join together by covalent bonding  All the bonds are covalent  This produces giant covalent structures not simple molecules  Also called a macromolecular structure  Diamond, graphite and silicon dioxide have giant covalent structures

4.  Diamond has a giant covalent structure  Diamond is made from carbon atoms  Each carbon atom is covalently bonded to four other carbon atoms  All the carbon atoms are held together by strong covalent bonds C C C C C Carbon atom Strong covalent bond

7. Diamond Mine is located in Russia

8.  Diamond only contains strong covalent bonds  Therefore it is very hard and chemically unreactive  It has high melting and boiling points as a lot of energy is needed to break the strong covalent bonds  Diamond does not conduct electricity as it has no free electrons or ions

9.  Uses of diamond:  Cutting tools and  Jewellery

11.  Silicon dioxide (SiO 2 ) has a giant covalent structure  Silicon dioxide has a similar structure to diamond  It contains silicon and oxygen atoms instead of carbon atoms  All the atoms are held together by strong covalent bonds

12.  Graphite has a giant covalent structure  Graphite contains only carbon atoms  Each carbon atom is covalently bonded to three other carbon atoms  The carbon atoms are arranged in layers  The carbon atoms in the layers are arranged in hexagons  The layers are held by intermolecular forces Strong covalent bond Weak forces

13. Strong covalent bonds between carbon atoms in the layers Weak intermolecular forces between the layers

14.  Each carbon atom is covalently bonded to three other carbon atoms  Therefore only three of the four electrons in the outer shell of the carbon atom (2,4) are used  This leaves one free electron on carbon  The layers in graphite contains delocalised electrons  The electrons can carry a current

15.  Graphite is soft and slippery  The layers can slide over each other because the weak intermolecular forces are easily broken  Graphite conducts electricity  It has high melting and boiling points as a lot of energy is needed to break the strong covalent bonds http://www.youtube.com/wat ch?v=1IyTMvH4wJU&feature=f vwrel

16.  Uses of graphite:  Pencils  The layers slide off and end up on the paper  Lubricant  Graphite is slippery and allows objects to move easily

17.  How do the different properties of diamond and graphite depend on their structures?