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The halogens for OCR GCSE Chemistry

The halogens

This page covers the following topics:

1. Melting and boiling points of halogens

Halogens form small covalent molecules with the formula Xโ‚‚ held together by van der Waals forces. Larger molecules can have stronger van der Waals interactions, increasing the energy needed to separate them from other molecules. Therefore, the melting and boiling points of halogens increase with an increasing atomic radius and the size of molecules as you travel down the group 7 of the periodic table. Due to different melting and boiling points, fluorine and chlorine at room temperature are gases, bromine - liquid and iodine - solid.

Melting and boiling points of halogens

1

Explain how does the melting point change going down the group 7 of the periodic table.

Going down the group 7 of the periodic table elements form larger molecules that can have stronger van der Waals interactions, increasing the energy needed to separate them from other molecules. Therefore, the melting point of halogens increases with an increasing atomic radius and the size of molecules as you travel down the group.

larger molecules โ†’ stronger van der Waals interactions โ†’ higher melting point

Explain how does the melting point change going down the group 7 of the periodic table.

2

Which halogen has the lowest boiling point?

Going down the group 7 of the periodic table elements form larger molecules that can have stronger van der Waals interactions, increasing the energy needed to separate them from other molecules. Therefore, the boiling point of halogens increases with an increasing atomic radius and the size of molecules as you travel down the group. Thus, the halogen with the lowest melting point is fluorine.

fluorine

Which halogen has the lowest boiling point?

3

Which halogen has a higher melting point than fluorine and is gas at room temperature?

The melting point of halogens increases with an increasing atomic radius and the size of molecules as you travel down the group 7 of the periodic table. Fluorine and chlorine at room temperature are gases, bromine - liquid and iodine - solid. The halogen that matches the description provided is chlorine.

chlorine

Which halogen has a higher melting point than fluorine and is gas at room temperature?

4

The melting point of fluorine is โˆ’220ยฐC and the melting point of bromine is โˆ’7.2ยฐC. Estimate the melting point of chlorine.

The melting point of halogens increases with an increasing atomic radius and the size of molecules as you travel down the group 7 of the periodic table. Thus, the melting point should be somewhere in between the melting point of fluorine and bromine, around between โˆ’120ยฐC and โˆ’80ยฐC.

โˆ’101ยฐC

The melting point of fluorine is โˆ’220ยฐC and the melting point of bromine is โˆ’7.2ยฐC. Estimate the melting point of chlorine.

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