In ZnS crystal , S2- occupy all corners and face centres while Zn2+ occupy alternate tetrahedral voids. If sum of radius of Zn2+ and S2- ion is 280 pm then the edge length of unit cell is

  • Option 1)

    342.8 pm

  • Option 2)

    646.6 pm

  • Option 3)

    280 pm

  • Option 4)

    121.2 pm

 

Answers (1)
S subam

Edge\; length=\frac{4}{\sqrt{3}}\left ( r_{Zm^{2+}} +r_{s^{2-}}\right )

                            =\frac{4}{\sqrt{3}}\left ( 280 \right )=646.6pm

 

 

Zinc blende structure (ZnS) -

{S^{2-} arrange in CCP

 

{Zn^{2+} found in 50% tetrahedral voids

 

Edge length = \frac{4}{\sqrt{3}} (r_{Zn^{2+}} + r_{S^{2-}})

 

Coordination number = 4:4

- wherein

Number or {S^{2-} = 4

Number of {Zn^{2+} = 4

Number of ZnS molecule per unit cell = 4

Example = AgCl , AgBr , CuCl , CuBr , etc

 

 


Option 1)

342.8 pm

This is incorrect

Option 2)

646.6 pm

This is correct

Option 3)

280 pm

This is incorrect

Option 4)

121.2 pm

This is incorrect

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