graphite and diamond?

Question

why is graphite soft and why does it have a high melting point
and why is diamond hard and also have a high melting point? why is diamond a poor conductor of electric current and graphite a good conductor?

Answer 1

Graphite n diamond r both ALLOTROPES of carbon (C), i.e., both have the same constituent element but exhibit different physical forms.

In graphite, atoms of C in a single crystal r arranged in a hexagonal ring in a single plane. The bonds between the atoms of 2 single crystals in different parallel planes r very weak. Thus, one plane of crystals can be easily made to slide over another plane, thereby making it soft. Whereas in diamond, each atom is surrounded by 4 other C atoms by covalent bonds, such that they form the 4 corners of a regular tetrahedron, which is 3D in structure. Thus, all the C atoms lie in different planes and cannot be made to slip over 1 another, making diamond the hardest substance on earth.

With respect to conductivity, in diamond, each C atom is surrounded by 4 other atoms by covalent bonds, leaving no electrons free, that could conduct elec. In graphite, each C atom is covalently bound to 3 other atoms, leaving 1 e- free per atom. These e- can be easily made to flow throgh graphite by applying p.d., n this makes graphite a good conductor.

As for m.p., I think neither of them melt. Diamond catches fire at 900C in air n 800C in O2, to form CO2 n leaving no ash. Graphite doesn't burn in air, but catches fore in O2 at 700C, forming CO2 n CO n a little ash. The weak covalent bonds in graphite account for the vaporization at less temp.

P.S. -- This has been quite a bit of typing practice for me.

Answer 2

it's all with the crystalline structure. they're all made of carbon, but the structure of the crystal varies, and that's what gives it its properties. check it out at

http://en.wikipedia.org/wiki/Carbon

Answer 3

This is somethin to ask your 8th grade science teacher..