Chemical Bonding

Chemical Bonding

1. Metallic bonding

   • All structures have a structure of a lattice of positive ions
   • free electrons = metallic bonding
   • Electrical conductivity- Free electrons carry negative charge so electric current can pass through when voltage is applied
   • Thermal conductivity- positive ions close together so they can pass the vibrations of hot ions to the next ion. free electrons move faster when heat is applied with heat so goes from cold to hot through the structure.

2. Ionic bonding

   • Excess electrons on outer shell of element will go to another element to complete its outer shell
   • Elements want a full outer shell
   • When an element gains an electron it becomes a negative charge( electron has a negative charge)
   • When an element looses an electron it becomes positively charged (electron has a negative charge)

3. Simple molecular bonding

   • Molecules are made when atoms share electrons forming a covalent bond.
   • Atoms share enough to fill their outer shell
   • Atoms can have double covalent bonds, each atom will share 4 electrons )2 pairs) - Carbon Dioxide
   • Covalent bonds are strong
   • each molecule is electrically neutral
   • Solid covalent bonds have low melting points

4. Giant covalant substances

   • Diamond and Graphite
   • High melting points, all atoms have strong covalent bonds
   • Carbon has 4 outer electrons, needs to share another 4 to complete its outer shell
   • In diamond each carbon atom is connected to 4 other carbon atoms
   • Graphite is a lubricant because it has mobile electrons between layers
   • Diamond is very hard as its has four covalent bonds

5. Carbon nanotubes

   • Molecular scale tubes of very thin graphite
   • Stronger than steel, and can conduct electricity better than copper
     • Strong because of the bonded hexagonal carbon sheets
     • Good conductor because of the free electrons