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Why do the melting/boiling points of the alkali metals decrease down the group and yet the melting/boiling points of the halogens increase down the group? What is the difference between the two groups that cause this variation?
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#2
The trend of the alkali metals is due to a weakening of their metallic bonds. As the atoms get bigger, the nuclei of the ions get further away from their free electrons, so the attraction is less.
The trend of halogens is due to an increase of van der Waals forces, caused by electrons shifting to one side.
This isn't required for GCSE science though, I believe.
The trend of halogens is due to an increase of van der Waals forces, caused by electrons shifting to one side.
This isn't required for GCSE science though, I believe.
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#3
(Original post by epaul)
Why do the melting/boiling points of the alkali metals decrease down the group and yet the melting/boiling points of the halogens increase down the group? What is the difference between the two groups that cause this variation?
Why do the melting/boiling points of the alkali metals decrease down the group and yet the melting/boiling points of the halogens increase down the group? What is the difference between the two groups that cause this variation?
For halogens (Group 7) all of the above is the exact opposite. They have 7 electrons and need to gain 1 to become stable. As the outer shell gets further from the attraction to the positive nucleus, this gets more difficult, so the smaller atoms are more reactive.
This is what we learn and I can only assume that more reactive elements are necessarily more volatile and require less energy to change state, so they have lower melting/boiling points. But it might be a good idea to not take this as fact
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(Original post by Dragolien)
The trend of the alkali metals is due to a weakening of their metallic bonds. As the atoms get bigger, the nuclei of the ions get further away from their free electrons, so the attraction is less.
The trend of halogens is due to an increase of van der Waals forces, caused by electrons shifting to one side.
This isn't required for GCSE science though, I believe.
The trend of the alkali metals is due to a weakening of their metallic bonds. As the atoms get bigger, the nuclei of the ions get further away from their free electrons, so the attraction is less.
The trend of halogens is due to an increase of van der Waals forces, caused by electrons shifting to one side.
This isn't required for GCSE science though, I believe.
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#5
(Original post by epaul)
I'm not really sure to be honest; some say it is required for GCSE and other say it's not. But hey, I'm interested anyway. Thank you 😊
I'm not really sure to be honest; some say it is required for GCSE and other say it's not. But hey, I'm interested anyway. Thank you 😊
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