Group 7: Halogens
The halogens are reactive non-metals in Group 7 that form salts with metals and get less reactive down the group.
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The halogens are reactive non-metals in Group 7 that form salts with metals and get less reactive down the group.
- Fluorine is the most reactive
- They have seven outer electrons
- A more reactive halogen displaces a less reactive one
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Group 7: Halogens?
Within Chemistry, which covers atoms, bonding, reactions, the periodic table, organic chemistry and the chemistry of everyday life, this topic explains Group 7: Halogens. Chemistry links what you can see in the lab to the particles and bonds behind it, so each topic here shows that link in a model.
Check that you can explain Group 7: Halogens in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Group 7: Halogens helps you explain why substances behave as they do, from cleaning products and food to medicines.
Group 7: Halogens in detail
The halogens (fluorine, chlorine, bromine, iodine) are non-metals with seven outer electrons, which form diatomic molecules such as Cl₂. Going down the group, they change from a pale yellow gas (fluorine) and green gas (chlorine) to a red-brown liquid (bromine) and a grey solid (iodine), and melting and boiling points increase.
They react with metals to form ionic salts containing a 1− ion. Reactivity decreases down the group, because the outer shell is further from the nucleus and attracts an extra electron less strongly, so a more reactive halogen displaces a less reactive one from its salt solution. Chlorine is used to sterilise water.
How the interactive helps you understand Group 7: Halogens
Watch the reaction model in the interactive. Use any sliders or buttons it offers to change the values and see how the reaction model responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Group 7: Halogens.
Real-life uses and examples
- Explain Group 7: Halogens in an exam by linking the particles involved to what you observe.
- Use Group 7: Halogens to explain what happens in a lab experiment and why.
- Link Group 7: Halogens to everyday products such as cleaning agents, food and medicines.
Common mistakes to avoid
- Mixing up the names of substances or ions when you describe Group 7: Halogens.
- Describing what happens without explaining the particles or bonds involved.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Group 7: Halogens
What is Group 7: Halogens?
The halogens are reactive non-metals in Group 7 that form salts with metals and get less reactive down the group.
What are the most important points about Group 7: Halogens?
The main points are: Fluorine is the most reactive; They have seven outer electrons; A more reactive halogen displaces a less reactive one.
Why is Group 7: Halogens useful?
Understanding Group 7: Halogens helps you explain why substances behave as they do, from cleaning products and food to medicines.
How can I practise Group 7: Halogens?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Group 7: Halogens?
Related topics in Chemistry include Metals and Non-Metals, Metallic Bonding, Giant Covalent Structures.