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    Properties of Group 7

    I can describe patterns in the properties of group 7 elements and explain how these are determined by their electron structures.

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      Properties of Group 7

      I can describe patterns in the properties of group 7 elements and explain how these are determined by their electron structures.

      Lesson details

      Key learning points

      1. Group 7 elements are very reactive and their reactivity decreases down the group.
      2. Moving down Group 7 elements, atomic mass, density, and melting and boiling points increase.
      3. In chemical reactions, atoms of Group 7 elements gain one outer electron making just full electron shells.
      4. Going down Group 7, the force attracting an extra electron reduces with the distance of each shell from the nucleus.
      5. Halogens are elements, halides are salts.

      Keywords

      • Salts - are ionic compounds formed from positive and negative ions electrostatically attracted to each other.

      • Halogens - are reactive non-metallic elements in Group 7 of the periodic table which react with metals to form salts.

      • Halides - are the name of salts formed from halogens, e.g sodium chloride (NaCl).

      • Diatomic - element consists of two atoms of the same type, chemically bonded together.

      Common misconception

      Pupils often forget that the halogens are diatomic molecules.

      Explanation of the bonding to form molecules helps to explain why they exist as diatomic molecules.

      Writing the formula and calculation of the molecular mass by the pupils helps to show that this is double the atomic mass.
      Teacher tip

      Equipment

      None required.

      Licence

      This content is © Oak National Academy Limited (2026), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

      Lesson video

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      Prior knowledge starter quiz

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      6 Questions

      Q1.
      Match the following elements to their symbols.

      Correct Answer:Fluorine,F

      F

      Correct Answer:Chlorine,Cl

      Cl

      Correct Answer:Iodine,I

      I

      Correct Answer:Astatine,At

      At

      Correct Answer:Bromine,Br

      Br

      Q2.
      Identify potassium bromide from the list of chemical formulae

      Correct answer: KBr
      PBr
      KB
      BrP
      PbR

      Q3.
      What is the name given to Group 7 on the periodic table?

      Salts
      Metals
      Noble gases
      Correct answer: Halogens
      Alkali metals

      Q4.
      Which term is used to correctly describe an element that exists as a molecule composed of two atoms bonded together?

      Monatomic
      Correct answer: Diatomic
      Biatomic
      Bionic
      Dibond

      Q5.
      Which of these Group 7 elements will have the largest relative atomic mass?

      Correct answer: I
      F
      Br
      Cl

      Q6.
      Which Group 7 element has 35 protons, 35 electrons and 45 neutrons?

      Iodine
      Chlorine
      Correct answer: Bromine
      Fluorine

      Assessment exit quiz

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      6 Questions

      Q1.
      Match the halogen to an example of one of its uses.

      Correct Answer:Fluorine,added to toothpaste to prevent tooth decay

      added to toothpaste to prevent tooth decay

      Correct Answer:Chlorine,added to tap water to kill harmful microbes present

      added to tap water to kill harmful microbes present

      Correct Answer:Iodine,as an antiseptic to treat wounds

      as an antiseptic to treat wounds

      Q2.
      When a bromine atom forms a bromide ion, it gains an electron. Which is the correct ion?

      Correct answer: Br ⁻
      Br²⁻
      Br₂
      Br₂ ⁻

      Q3.
      Match the melting point to the correct halogen.

      Correct Answer:Fluorine,-219.6°C

      -219.6°C

      Correct Answer:Chlorine,-101.5°C

      -101.5°C

      Correct Answer:Bromine,-7.3°C

      -7.3°C

      Correct Answer:Iodine,113.7°C

      113.7°C

      Correct Answer:Astatine,302.0°C

      302.0°C

      Q4.
      Calculate the relative molecular mass of a bromine molecule.

      Correct Answer: 160

      Q5.
      Choose a halogen from the list which would displace chlorine from potassium chloride.

      Bromine
      Correct answer: Fluorine
      Astatine
      Iodine

      Q6.
      Select the responses which explain why bromine is more reactive than iodine.

      Correct answer: Iodine is a larger atom than bromine.
      Correct answer: Bromine's outer electron shell is closer to the positively charged nucleus.
      Correct answer: Outer electrons in bromine are more strongly attracted to the nucleus.
      Bromine atoms gain electrons more easily from all other elements.

      Lesson appears in

      UnitChemistry / Groups of the periodic table

      AQAChemistry

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      EdexcelChemistry

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      UnitCombined science / Groups of the periodic table

      AQACombined science

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      EdexcelCombined science

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