Question

How will you distinguish between the following pairs of terms :

(i) Tetrahedral and octahedral voids

(ii) Crystal lattice and unit cell

Answer 1

(i) Difference between tetrahedral octahedral voids :

$\begin{array}{cccc}& \text{Tetrahedral void}& & \text{Octahedral void}\\ 1.& \text{The vacant space among}& 1.& \text{The void formed by two}\\ & \text{four spheres having}& & \text{equilateral triangles with}\\ & \text{tetrahedral arrangement is}& & \text{apices in opposite direction}\\ & \text{called tetrahedral void.}& & \text{is called octahedral void}\\ & & & \text{and it is surrounded by six}\\ & & & \text{spheres at the vertices of}\\ & & & \text{a regular octahedron.}\\ 2.& \text{For N spheres in the close}& 2.& \text{For N spheres in the close}\\ & \text{packed arrangement, no.}& & \text{packed arrangement, the}\\ & \text{of tetrahedral voids = 2N.}& & \text{no. of octahedral voids=N.}\end{array}$

(ii) Difference between crystal lattice and unit cell :

$\begin{array}{cc}\text{Crystal lattice}& \text{Unit cell}\\ \text{It is the three dimensional}& \text{It is the smallest repeating}\\ \text{arrangement of atoms/}& \text{pattern of a crystal lattice}\\ \text{ions/molecules of a solid.}& \text{which when repeated in three}\\ & \text{dimensions generates the lattice.}\end{array}$