Solid State — Chemistry STD 12 Science — Question

(1) Tetrahedral void : The vacant space or void among four constituent particles having tetrahedral arrangement in the crystal lattice is called tetrahedral void.

The arrangement of four spheres around the void is tetrahedral. A tetrahedral void is formed when a triangular void made by three coplanar spheres is in contact with fourth sphere above or below it.

(2) Characteristics of tetrahedral void :

• The volume of the void is much smaller than that of atom or sphere.
• Larger the size of sphere, more is the size of void.
• If R is the radius of the constituent atom, then the radius of the tetrahedral void is 0.225 R.
• Coordination number of tetrahedral void is four.
• There are two tetrahedral voids per sphere, in the crystal lattice. If the number of closed packed spheres is N then the number of tetrahedral voids is 2N.