CBSE Class 12-science Chemistry The Solid State
Crystalline and Amorphous Solids
An amorphous solid is a substance whose constituent particles do not possess a regular orderly arrangement.
Crystalline solids have a sharp melting point.
Three Dimensional Packing
Cubic close packing has ABCABC arrangement
There are 2 types of voids in 3 dimensional close packing- Tetrahedral and Octahedral voids.
A Unit cell having lattice points at the centre of each face in addition to the lattice points at the corners is called face centred unit cell.
A Unit cell having lattice points at the centre of the body in addition to the lattice points at the corners is called body centred unit cell.
Number of atoms per unit cell in a body centred cubic unit cell is 2
Number of atoms per unit cell in a face centred cubic unit cell is 4
Dimensions of Unit Cells
Edge length of a simple cubic cell is twice the radius
Mass of the unit cell is equal to the product of number of atoms in the unit cell and mass of each atom
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