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In a face centred cubic lattice, atom A occupies the corner positions and atom B occupies the face centre positions. If one atom of B is missing from one of the face centred points, the formula of the compound is

  • Option 1)

    A_{2}B\;

  • Option 2)

    \; AB_{2}\;

  • Option 3)

    \; A_{2}B_{3}\;

  • Option 4)

    \; A_{2}B_{5}

 

Answers (1)

best_answer

As we learnt in

No. of atoms(z) for face centered unit cell -

Lattice points: at corners and face centers of unit cell.

For face centered cubic (FCC), z=4.

- wherein

 

 

No. of atoms(z) for simple cubic unit cell -

Lattice points: at corners

For simple cubic (SC), z=1

- wherein

 

Number of atom A per unit cell =8\times \frac{1}{8}=1

Number of atom B per unit cell =5\times \frac{1}{2}=\frac{5}{2}

AB5/2 i.e. A2B5

Correct option is 4.

 

 


Option 1)

A_{2}B\;

This is an incorrect option.

Option 2)

\; AB_{2}\;

This is an incorrect option.

Option 3)

\; A_{2}B_{3}\;

This is an incorrect option.

Option 4)

\; A_{2}B_{5}

This is the correct option.

Posted by

prateek

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