Question

Diamond is hard because

• A. all the four valence electrons are bonded to each carbon atoms by covalent bonds
• B. it is a giant molecule
• C. it is made up of carbon atoms
• D. it cannot be burnt

Hint:

Diamond is the hardest because it has a 3D covalent network where each carbon forms four strong bonds.

Answer 1

The Correct Option is A

Step 1: Structure of diamond.
In diamond, each carbon atom is sp\(^3\) hybridized and forms four strong covalent bonds with four neighbouring carbon atoms.
Step 2: Formation of rigid 3D network.
These covalent bonds extend throughout the crystal forming a rigid three-dimensional tetrahedral lattice.
Step 3: Reason for hardness.
Since every carbon is strongly bonded in all directions, it is extremely difficult to break the structure, hence diamond is very hard.
Step 4: Conclusion.
Thus hardness is due to strong covalent bonding of all four valence electrons.
Final Answer:
\[ \boxed{\text{(A) all four valence electrons form strong covalent bonds}} \]