Why does the melting point of graphite is higher than diamond?

[abi.ayan]

In diamond valence electrons are fully covalently bonded.But in graphite only three are covalently bonded while one electron is freely moving.So it seem that melting point of diamond should be higher than that of graphite because in diamond we should break four covalent bonds while in graphite only three bonds.Can anyone explain this pls?

 

[janhaa]

The melting point of graphite is slightly larger than the melting point of diamond, because in graphite C-C bonds have a partial double bond character and hence are stronger and more difficult to break.

There are also Van der Waals forces between the layers of graphite but these are relatively weak in comparison to a covalent bond. These weak forces allows layers of graphite to slide past each other...

 

[pearmtn]

check out this site for a detailed explanation:

http://invsee.asu.edu/nmodules/carbonmod/bonding.html

 

[snorkack]

What are you claiming graphite´s melting point to be? It is still remarkably hard to measure!

 

[chandi2398]

why does the melting point of graphite is higher than diamond? I have the same problem. please can anyone explain this?

 

[adjacent]

why does the melting point of graphite is higher than diamond? I have the same problem. please can anyone explain this?

This thread is more than 6 months old.
Please read the above posts.

 

[snorkack]

why does the melting point of graphite is higher than diamond? I have the same problem. please can anyone explain this?

So starting with the same question: what do you claim graphite melting point is?

 

[Chase]

Diamond doesn't even melt, it burns. Even still the "melting" point of diamond is 4300K whereas graphite is 3948K

 

[adjacent]

Even still the "melting" point of diamond is 4300[STRIKE]K[/STRIKE] whereas graphite is 3948[STRIKE]K[/STRIKE]

Corrected


It is possible to melt diamonds. However it is impossible to do at standard temperatures and pressures like that at SATP. It has been done by the Z-Machine at the Sandia National Laboratories by using a pressure of 10 million times normal Atmospheric pressure. To create the pressure, the machine's magnetic fields hurled small plates at the diamond
at 34 kilometers per second (21 miles per second), or faster than the Earth orbits the Sun.
Unfortunately in open air, the fact that is it large network of covalently bonded carbons make it extremely hard to melt in the first place. Secondly, diamond at high temperatures will not melt, rather it will prefer to burn, as characteristic of all carbon allotropes. A diamond will burn or oxidize when exposed to a hot flame in the presence of oxygen, for example an oxygen torch with a temperature of 800 degrees C (1,472 degrees F), according to The Merck Index, a standard chemistry reference work.


but it can be melted in the absence of air (or in vacuum) at a very very very high temperature
A melted diamond is uncommon.

 

[snorkack]

It is possible to melt diamonds. However it is impossible to do at standard temperatures

Obviously objects that are solid at standard temperatures and pressures do not melt at standard temperatures generally.

Secondly, diamond at high temperatures will not melt, rather it will prefer to burn, as characteristic of all carbon allotropes. A diamond will burn or oxidize when exposed to a hot flame in the presence of oxygen, for example an oxygen torch with a temperature of 800 degrees C (1,472 degrees F), according to The Merck Index, a standard chemistry reference work.


but it can be melted in the absence of air (or in vacuum) at a very very very high temperature

No, diamond cannot be melted in vacuum. Solid diamond at low pressures and high temperatures is converted to solid graphite without melting.