Group 7 (Halogens)
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Physical properties of Group 7 elements
The Group 7 elements are the halogens: fluorine, chlorine, bromine, iodine and astatine, all poisonous non-metals with seven electrons in their outer shell. Each halogen forms diatomic molecules, meaning two atoms joined by a single covalent bond. At room temperature the group spans every state, from fluorine and chlorine as gases, through bromine as a liquid, to iodine as a solid.
What you know already
From Group 7 (Halogens) you already know that these reactive non-metals sit one column left of the noble gases, each with seven outer electrons. This note adds their states and colours at room temperature, the melting and boiling point trend, how the pattern predicts any member of the group, and how displacement reactions prove the reactivity order.
Key points of understanding
- On descending the group, the halogens melt and boil at steadily higher temperatures.
- Larger atoms give stronger intermolecular forces, so more energy is needed to overcome them.
- Fluorine is a yellow gas, chlorine a pale yellow-green gas, bromine a red-brown liquid and iodine a grey solid.
- The colours of the halogens darken as you descend the group.
- In solution, chlorine appears pale green, bromine orange and iodine dark brown.
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1.Physical properties of Group 7 elements
The Group 7 elements are the halogens: fluorine, chlorine, bromine, iodine and astatine, all poisonous non-metals with seven electrons in their outer shell. Each halogen forms diatomic molecules, meaning two atoms joined by a single covalent bond. At room temperature the group spans every state, from fluorine and chlorine as gases, through bromine as a liquid, to iodine as a solid.
Key points
- On descending the group, the halogens melt and boil at steadily higher temperatures.
- Larger atoms give stronger intermolecular forces, so more energy is needed to overcome them.
- Fluorine is a yellow gas, chlorine a pale yellow-green gas, bromine a red-brown liquid and iodine a grey solid.
- The colours of the halogens darken as you descend the group.
- In solution, chlorine appears pale green, bromine orange and iodine dark brown.
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