3.2 (b) Molecules and covalent bonds
Single covalent bond: a bond where 2 non-metals share a pair of electrons to get full-outer shells as seen in H2, Cl2, H2O, CH4 and HCl represented by a line connecting the two symbols e.g. H-H
Double bond is when 4 electrons are shared (two from each atom) and a triple bond is when 6 are shared (3 from each atom) e.g. C=C and N≡N
| Volatility (forms vapour) | Solubility | Electrical conductivity | |
| Ionic compound | low | usually soluble | when molten or in solution |
| Covalent compound | high | the majority do not dissolve | none (except graphite) |
Know how to draw the following structures: N2, C2H4, CH3OH, and CO2
Important things to note: covalent bonds are weak, and ionic bonds are strong. When you melt an ionic solid you break up the compound into ions, so it takes more energy, therefore ionic compounds have higher melting points. When you melt a covalent solid, the molecules are broken up from each other but are still bonded (e.g. when you melt ice you get H2O molecules but in a liquid, but melting NaCl gives you a molten mixture of Na+ and Cl- ions).