Describe and explain the trends in the physical properties below:
| element | bond dissociation enthalpy/kJmol-1 | atomic radius/nm | electron affinity | Boiling temperature/oC |
| fluorine | 158 | 0.072 | 4.0 | -188 |
| chlorine | 242 | 0.099 | 3.0 | -34.7 |
| bromine | 193 | 0.114 | 2.8 | 58.8 |
| iodine | 151 | 0.133 | 2.5 | 184 |