Diamond and graphite are both carbon. Diamond is hard because:

  1. it is amorphous
  2. each atom is bonded to four others in a rigid 3-D lattice
  3. it is a polymer
  4. it has free molecules
Answer

B) each atom is bonded to four others in a rigid 3-D lattice

Strong covalent bonds in three dimensions. SLO P-11-B-22 · Understanding

Physics MCQ · More Deformation of Solids MCQs · Practise