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Author Topic: What determines the boiling points of aluminium and magnesium?  (Read 11690 times)

Offline EvilFrog

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why the boiling point of aluminium is more than magnesium by 10C only?


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« Last Edit: 24/10/2009 18:57:54 by chris »


 

Offline lightarrow

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why the boiling point of aluminium is more than magnesium by 10C only?
Control again your data...
(hint: 1400C is probably different from 10C  ;))


http://en.wikipedia.org/wiki/Boiling_points_of_the_elements_(data_page)

which doesn't work because the last parenthesis doesn't appear as part of the link ( ??? ??? ???) so you have to find, listed, here:

http://en.wikipedia.org/wiki/Chemical_elements_data_references
« Last Edit: 20/10/2009 20:25:29 by lightarrow »
 

Offline Bored chemist

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I think he means the melting points which are very similar. On the other hand the metals are quite similar in many respects so the similarrity of the melting points doesn't shock me.
 

Offline lightarrow

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I think he means the melting points which are very similar. On the other hand the metals are quite similar in many respects so the similarrity of the melting points doesn't shock me.
Ah, ok. If that is the question, I would say that the difference is due, in part, from the lower atomic radius of Al (the coordination number of the crystal structure is 12 in both cases).
 

Kiran The King Kai

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I think he means the melting points which are very similar. On the other hand the metals are quite similar in many respects so the similarrity of the melting points doesn't shock me.
BC it's She ! LOL
 

Offline EvilFrog

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My question is, why the boiling point of these two elements is differ by about 10C only?? what cause this??
 

Offline Bored chemist

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I think he means the melting points which are very similar. On the other hand the metals are quite similar in many respects so the similarrity of the melting points doesn't shock me.
BC it's She ! LOL

Oops!
No offense intended. I'm a chemist not a biologist so gender differences in frogs (evil or otherwise) are not my field.


However, the boiling points of those two elements differ by a lot more thna 10 degrees (as was already pointed out).
The melting points differ by about 10C.
 

Offline lightarrow

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My question is, why the boiling point of these two elements is differ by about 10C only?? what cause this??
And my (already made) answer is: do you know that you have made a mistake?
 

Offline EvilFrog

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oops.. sorry, is melting point. "lower atomic radius of Al"? then how about magnesium. sorry a... my english is not pro. my chemistry also not pro. so can u all explain in the way that is more easy for me to understand?
« Last Edit: 21/10/2009 11:21:48 by EvilFrog »
 

Offline lightarrow

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oops.. sorry, is melting point. "lower atomic radius of Al"? then how about magnesium. sorry a... my english is not pro. my chemistry also not pro. so can u all explain in the way that is more easy for me to understand?
As a general rule, the bigger are atoms or ions in a solid structure, the lower is the force which binds them (at equal ion charges, ecc). In a metallic bonding, for example, the (almost) free electrons behave as a sort of "glue" because they attract the positively charged atoms; the bigger they are, the less their centres can approach the electrons and so the less strong is the bonding. The strenght of the bonding also depends on the packing of atoms, but in this case is the same, because Mg forms a compact exagonal lattice, the Al a face-centered cubic one, and they have the same coordination number (12) and the same packing efficiency (74%). The strenght also depends on the number of electrons in the conduction band and on the availability of bonding orbitals in the atom, infact transition metals have higher melting points for this last reason. Anyway, the metallic strenght is more represented by the metal boiling point than from the melting point.
« Last Edit: 21/10/2009 20:07:46 by lightarrow »
 

Offline EvilFrog

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em.. sorry, what is coordination number and infant transition metal?
 

Offline Bored chemist

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The coordination number is the number of "nearest neighbours" an atom has in a structure.
The "infact transition.." is a typo and should be "in fact transition metals have higher melting points for this last reason"
 

Offline lightarrow

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The coordination number is the number of "nearest neighbours" an atom has in a structure.
The "infact transition.." is a typo and should be "in fact transition metals have higher melting points for this last reason"
Thanks for the correction.
 

Offline lightarrow

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In case you wonder, packing efficiency is the percent of the total volume which is effectively taken up by the atoms: if you take, let's say, a one litre box and you fill it with small, all equal, objects, if they take up 0.74 litres, the packing efficiency of those objects is 74%.
 

Offline EvilFrog

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"number of "nearest neighbours" an atom has in a structure" = number of bonding with other atoms?
 

Offline lightarrow

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"number of "nearest neighbours" an atom has in a structure" = number of bonding with other atoms?
In general you can say that there is an 'interaction', not exactly a 'bonding' between the atoms; anyway, the concept is that.
 

Offline EvilFrog

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thanks for explain..

best wishes. :)
 

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