Class 12 Chemistry The Solid State Number of atoms per unit cell in Body Centered Cubic Unit Ce

Number of atoms per unit cell : Body Centered Cubic Unit Cell

In a body-centered cubic (bcc) unit cell, the atoms are present in the body-center besides the ones that are at its corners that wholly belongs to the unit cell in which it is present. Thus in a body-centered cubic (bcc) unit cell:

8 corners X 1/8 per corner atom =   8 * 1/8           = 1 atom

1 body center atom = 1 X 1                              = 1 atom

Total number of atoms per unit cell                   = 2 atoms

 

Question: Niobium crystallises in body-centred cubic structure. If density is 8.55 g cm-3, calculate atomic radius of niobium using its atomic mass 93 u. 

Answer: Density = 8.55 gcm-3

Consider length of the edge = a cm

Number of atoms per unit cell, Z = 2

M = 93 u

Using the formula

 

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