Physical Properties of Halogens
- All group 17 elements are non-metals. Therefore they are heat and electricity insulator.
- The table below shows the electron arrangement and physical properties of group 17 elements.
|Name||Colour||Melting point||Boiling point|
|Fluorine||pale yellow gas||-220ºC||-188ºC|
|Chlorine||Yellowish green gas||-102ºC||-34ºC|
|Bromine||dark red liquid, brown vapour||-7ºC||59ºC|
|Iodine||black solid, purple vapour||114ºC||184ºC|
|Astatine||black solid, dark vapour||302ºC||380ºC|
Size of Atom and Density
- The atomic size of group 17 elements increases down the group.
- This is due to the increase of the number of electron shell down the group.
- The density of group 17 elements also increase down the group.
- This is because the rate of increment of the atomic mass is higher than the rate of increment of the volume.
Melting Point and Boiling Point
- As shown in the graph to the right, the melting points and boiling increase steadily down the group.
- The physical state at room temperature also change from gas to liquid and then to solid.
- This is because of the intermolecular attractive force (van der Waals force) increase with increasing size of atom or molecule.