why deos magnesium show hcp but not copper

Asked by banga71 | 14th Apr, 2017, 10:52: AM

Expert Answer:

  • The crystal structure adopted by a particular metal at a given temperature and pressure will be the structure which provides for the minimisation of free energy.
  • The atoms of the metal will form arrangements which ensure that the electron orbitals that bond them have the repulsion/attraction due to bond length all contribute to the lowest energy state. 
  • Each metal has a slightly different metallic radiuswhich is defined as half of the distance between the two adjacent metal ions in the metallic lattice.
  • Depending on the metallic radius, the lowest energy state would be achieved by different atomic arrangements. 
  • For the alkaline earth metals with the smaller metallic radii (beryllium and magnesium), the lowest energy state is the HCP structure.
  • To achive lowest energy level, copper forms FCC.

Answered by Prachi Sawant | 15th Apr, 2017, 09:23: PM