Physical State of the Halogens

Specification Point 6.6:
  • Recall the colours and physical states of chlorine, bromine and iodine at room temperature.
  • The halogens are the Group 7 non-metals that are poisonous and include fluorine, chlorine, bromine, iodine and astatine. 
  • Halogens are diatomic, meaning they form molecules of two atoms. 

PT Group 7, Edexcel GCSE Chemistry

The alkali metals lie on the far right-hand side of the Periodic table

  • At room temperature (20ºC), chlorine is a gas, bromine is a liquid and iodine is a solid.

States of Halogens, Edexcel GCSE Chemistry

The physical state of the halogens at room temperature

  • The halogens become darker as you go down the group.
  • Chlorine is pale green, bromine is red-brown and iodine is black.

Colours of Halogens 1

The colours of the halogens

Trend in Physical Properties of the Halogens

Specification Point 6.7:
  • Describe the pattern in the physical properties of the halogens, chlorine, bromine and iodine, and use this pattern to predict the physical properties of other halogens.

Melting and Boiling Point

  • The melting and boiling points of the halogens increases as you go down the Group.
  • This is due to increasing intermolecular forces as the molecules get bigger moving down the group.
  • Hence more energy is required to overcome these forces.

Mp and BP Halogens, Edexcel GCSE Chemistry

Graph showing the increase in melting and boiling points of halogens moving down Group 7

Physical States

  • Fluorine is at the top of Group 7 so will have the lowest melting and boiling point.
  • Astatine is at the bottom of Group 7 so will have the highest melting and boiling point.
  • Any halogens above chlorine will be gases due to low boiling points and those below iodine will be solid due to high boiling points.

States (2) Halogens, Edexcel GCSE Chemistry

Diagram showing how the physical state of the halogens changes with increasing boiling point

Colour

  • The colour of the halogens becomes darker as you go down the Group.
  • Fluorine is at the top of Group 7 so the colour will be lighter, so fluorine is yellow.
  • Astatine is at the bottom of Group 7 so the colour will be darker, so astatine is black.

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Edexcel GCSE Chemistry Notes

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Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.