Physical Properties of Halogens

  1. All group 17 elements are non-metals. Therefore they are heat and electricity insulator.
  2. Table below shows the electron arrangement and physical properties of group 17 elements.
Name Proton Number Electron arrangement Colour Melting point Boiling point
Fluorine
9
2.7 pale yellow gas -220ºC -188ºC
Chlorine
17
2.8.7 Yellowish green gas -102ºC -34ºC
Bromine
35
2.8.18.7 dark red liquid, brown vapour -7ºC 59ºC
Iodine
53
2.8.18.18.7 black solid, purple vapour 114ºC 184ºC
Astatine
85
2.8.18.32.18.7 black solid, dark vapour 302ºC 380ºC

Size of Atom and Density

  1. The atomic size of group 17 elements increases down the group.
  2. This is due to the increase of number of electron shell down the group.
  3. The density of group 17 elements is also increases down the group.
  4. 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


  1. As shown in the graph to the right, the melting points and boiling increase steadily down the group.
  2. The physical state at room temperature also change from gas to liquid and then to solid.
  3. This is because the intermolecular attractive force (van der Waals force) increase with increasing size of atom or molecule.

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