3.6 The elements of Group 7
Summary: Have you ever smelled chlorine in tap water? Chlorine and its compounds do an important job. Tiny amounts destroy dangerous bacteria, making water safe to drink and swim in. Tags: science oxford-science student-book-7 chemistry Created: 2026-05-19 Last Updated: 2026-05-19
After this topic, you will be able to:
- describe the physical properties of the Group 7 Elements
- use data from tables or bar charts to describe patterns in the melting and boiling points of the Group 7 elements
- use patterns to predict reactions of the Group 7 elements with iron.
Think back
- State whether the elements on the right of the Periodic Table are metals or non-metals.
- List two physical properties of a typical non-metal.
- Write the names of the elements with these Chemical Symbols: F, Cl, Br, I. Use the Periodic Table to help you.
Key idea The elements in Group 7 of the Periodic Table are non-metals. They are also called halogens. From top to bottom of Group 7, melting point and boiling point increase.
Key words Group 7, halogen
Have you ever smelled chlorine in tap water? Chlorine and its Compounds do an important job. Tiny amounts destroy dangerous bacteria, making water safe to drink and swim in.
Are Group 7 elements like other non-metals?
Chlorine is in Group 7 of the Periodic Table. Figure 1 shows that the other elements of the group are fluorine, bromine, iodine, and astatine. The Group 7 elements are also called halogens.
Figure 1Group 7 is second from the right of the Periodic Table.
Figure 2 shows that the colours of the halogens get darker from top to bottom of the group.
Figure 2Chlorine, bromine, and iodine. Full text alternative to the content
Like most non-metals, the halogens have low melting points. At room temperature:
- chlorine is a pale green gas
- bromine is a dark red liquid – some of the liquid may evaporate as an orange gas
- iodine is a brittle, grey solid – some of the solid may sublime as a purple gas.
A Compare the colours and states of chlorine and iodine at room temperature.
Are there patterns in Group 7 properties?
Table 1 Melting and boiling points of the Group 7 elements. Element
Melting point in °C
Boiling point in °C
State at room temperature
fluorine
−220
−188
gas
chlorine
−101
−35
gas
bromine
−7
59
liquid
iodine
114
184
solid
In Group 7, melting point increases from top to bottom of the group.
B Describe the pattern in boiling points of the Group 7 elements.
Maths skills Look at the boiling point data in Table 1. Plot a bar chart of these data. Swap bar charts with a partner. Can you suggest improvements?
The Group 7 elements are reactive. Their Chemical Reactions are similar. For example, all the Group 7 elements react with iron.
Full text alternative to the content
Figure 3 shows that the reaction of chlorine with iron is very vigorous (strong). The reactions get less vigorous going down the group. This is different to Group 1, in which reactions get more vigorous from top to bottom.
Figure 3Iron reacts vigorously with chlorine.
C Predict the product of the chemical reaction of iron with fluorine.
Stretch zone
- Copy and complete the sentences. The Group 7 elements are also called alkali metals/halogens. They are on the left/right of the red line. This means they are metals/non-metals. Iron reacts with chlorine to make iron chloride/chlorine. The chemical reactions of the halogens with iron get less/more vigorous from top to bottom.
- Describe the colours and states at room temperature of chlorine, bromine, and iodine.
Stretch zone
- Compare the pattern in melting points of the Group 7 elements with the pattern in melting points of the Group 1 elements. Use data from Table 1 on this page and Table 1 on page 128.