Question

Diamond is formed by covalent bonding of carbon, but in covalent bond intermolecular force is less, then how diamond is the hardest naturally occurring substance? And also why in heavy atoms covalent bonds are weaker?
Plzz answer fast!!

Answer 1

Each carbon atom in diamond is joined to four other carbon atoms in such a way that one carbon atom is present at the centre of a regular tetrahedron while four others occupy the corners.Each atom at the corner is further attached to three more carbon atoms and so on ,as a result there is a strong bond between the atoms of carbon atoms because of which it is the hardest naturally occuring substance.

Answer 2

Covalent bonds can be strong or weak, that depends on the size of atoms in the bond and the number of bonds between the atoms.

  Carbon atoms are small and then there are 4 valency bonds between 4 carbon atoms and the central carbon atom.  This is because valency of carbon is 4.  The electrons are shared 50% by each.  So the covalency bonds are very strong.  They are arranged in a tetrahedron structure.  The carbon atoms are packed very closely and the gaps between the atoms is less because the atoms are small.

   Thus the packing density of carbon atoms in a diamond results in the most stable (after graphite) and strongest substance.
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Heavy atoms in covalent bonds are not so tightly bonded as the sizes of the atoms are large.  So electrons are loosely bound to the nucleus.  So the electron affinity will be less than that for a smaller atom.  For florine, being very small, the electron affinity will be very high, for example.