The total number of tetrahedral voids in the face centred unit cell is ................

(a) 6 (b) 8 (c) 10 (d) 12

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Solution

Answer (b). 8

The FCC unit cell contains 8 tetrahedral voids at the center of each 8 smaller cubes of a unit cell as shown below

Eight tetrahedral voids

per fcc unit cell

Each cube represented by numeric 1,2,3,4,5,6,7,8 center as shown above. Each cube contains one tetrahedral void at its body.

Number of atoms in fcc nuit cell = 4

Number of octahedral voids = 4

Number of tetrahedral voids = 8

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Similar questions

List-I (Solids)	List-II (Unit cell)	List-III (Coordination number)
(a) Rock salt	(p) Face-centred cubic, anion in tetrahedral void	(w) 6
(b) Fluorite	(q) Face-centred cubic, cation in octahedral void	(x) Cation (8), anion (4)
(c) Agl, ZnS	(r) Face-centred cubic, cation in alternate tetrahedral void	(y) Cation (4), anion (8)
(d) $N a_{2} O$	(s) Face-centred cubic, cation in tetrahedral void	(z) Cation (4), anion (4)

In the cubic close packing, the unit cell has

(a) 4 tetrahedral voids each of which is shared by four adjacent unit cell

(b) 4 tetrahedral voids within the unit cell

(d) 8 tetrahedral voids within the unit cells

The number of tetrahedral voids per unit cell in NaCl crystal is ......

(a) 4

(b) 8

(d) four times the number of octahedral voids

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