Group 7 (Oxford AQA IGCSE Combined Science Double Award): Revision Note

Exam code: 9204

Alexandra Brennan

Written by: Alexandra Brennan

Reviewed by: Stewart Hird

Updated on

Reactions of the Halogens

  • The elements in Group 7 are known as the halogens

  • The elements are:

    • Fluorine

    • Chlorine

    • Bromine

    • Iodine

    • Astatine

  • Group 7 elements:

    • Are non-metals that are poisonous

    • Are diatomic

      • This means that they form molecules made of two atoms

      • The halogen atoms share electrons in a single covalent bond between them

      • These molecules are written as as F2, Cl2, etc.

  • React with metals to form ionic compounds

    • The halogens form halide ions with a charge of -1

  • All halogens have similar reactions as they each have seven electrons in their outermost shell

The electron structure of Group 7 elements

Group 7 element electronic configurations, IGCSE & GCSE Chemistry revision notesGroup 7 element electronic configurations, IGCSE & GCSE Chemistry revision notes
The atoms of the elements of Group 7 all have 7 electrons in their outer shell
  • There are clear trends in reactivity, melting / boiling point and colour going down Group 7

  • Moving down Group 7:

    • The reactivity of the halogens decreases

      • This pattern in the reactivity of the halogens can be observed by their displacement reactions

    • The melting / boiling point of the halogens increase

    • The colour of the halogens gets darker

Melting and boiling points down Group 7

  • The melting / boiling points increase going down Group 7 because:

    • The atoms become larger

    • This means that there is an increase in intermolecular forces

    • So, more energy is required to overcome the increased intermolecular forces

    • This means that the melting / boiling point is higher

The melting and boiling points of the halogens

A bar chart showing the increase in melting and boiling points of the halogens going down Group 7
Going down Group 7, the melting and boiling points increase
  • The melting / boiling points affect the physical state of the halogens

  • This is seen as a trend going down Group 7

    • At room temperature (20 °C), the physical states of the halogens are:

      • Fluorine and chlorine are gases

      • Bromine is a liquid

      • Iodine is crumbly solid

Colour down Group 7

  • The colours of the halogens become darker going down Group 7

The colours of the halogens

Particle diagrams showing the halogens getting darker in colour going down Group 7.  Chlorine is pale green, bromine is orange-brown and iodine is grey-black
Going down Group 7, the state of the halogens changes

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Alexandra Brennan

Author: Alexandra Brennan

Expertise: Chemistry Content Creator

Alex studied Biochemistry at Newcastle University before embarking upon a career in teaching. With nearly 10 years of teaching experience, Alex has had several roles including Chemistry/Science Teacher, Head of Science and Examiner for AQA and Edexcel. Alex’s passion for creating engaging content that enables students to succeed in exams drove her to pursue a career outside of the classroom at SME.

Stewart Hird

Reviewer: Stewart Hird

Expertise: Chemistry Content Creator

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.

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