Chemistry Class Twelve

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Solid State

Packing Efficiency of Close Packed Structure - 1

Both ccp and hcp are highly efficient lattice; in terms of packing. The packing efficiency of both types of close packed structure is 74%, i.e. 74% of the space in hcp and ccp is filled. The hcp and ccp structure are equally efficient; in terms of packing.

The packing efficiency of simple cubic lattice is 52.4%. And the packing efficiency of body centered cubic lattice (bcc) is 68%.

Calculation of pacing efficiency in hcp and ccp structure:

The packing efficiency can be calculated by the percent of space occupied by spheres present in a unit cell.

Solid state 4

Let the side of an unit cell = a

And diagonal AC = b

packing efficiecny of hcp and ccp

Now, in ∆ ABC,

AB is perpendicular, DC is base and AC is diagonal

Solid state 5
Solid state 6

Thus,packing efficiency of hcp or ccp structure=74%

Packing efficiency of body centered cubic (bcc) structure:

packing efficiecny of bcc

In body centered cubic unit cell, one atom is present in body center apart from 4 atoms at its corners. Therefore, total number of atoms present in bcc unit cell is equal to 2.

Let a unit cell of bcc structure with side a.

Let FD (diagonal) = b and diagonal AF = c

Let the radius of atom present in unit cell = r

Now, in ∆EFD

Solid state 7

After subtituting the value of a from equation (vi) we get

Solid state 8

Thus,packing efficiency of bcc structure=68%


Previous            Next
Solid State - Introduction
Solid State - Crystal Lattice
Solid State - Close Packing Structure
Solid State - Efficiency of Close Packing Structure - 2
Solid State - Imperfections in Solids - Crystal Defects
Solid State - Electrical and Magnetic Properties
Solid State - NCERT In Text Solution 1
Solid State - NCERT In Text Solution 2
Solid State - NCERT In Text Solution 3
Solid State - NCERT Exercise Solution (Part 1)
Solid State - NCERT Exercise Solution (Part 2)
Solid State - NCERT Exercise Solution (Part 3)
Solid State - NCERT Exercise Solution (Part 4)
Solid State - NCERT Exercise Solution (Part 5)

 
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