CBSE Class 12-science Chemistry The Solid State
What is a crystalline solid? What does a crystal lattice look like? Find out with TopperLearning’s CBSE Class 12 Science Chemistry The Solid State study materials. You will also learn about the dimensions of unit cells, imperfections in crystals, three-dimensional packing and packing efficiency in this Chemistry chapter.
Dive deeper into the concepts related to the solid state with our CBSE Class 12 Science Chemistry learning materials. Watch concept videos, read revision notes or practise textbook solutions during revision. To enable you to ace your Class 12 board exam, we provide previous years’ papers and solutions too. You can practise our solutions for previous years’ papers and sample papers, and hone your skills to write your prelim exams and final Chemistry exam with confidence.
Crystalline and Amorphous SolidsA crystalline solid is a substance whose constituent particles possess a regular orderly arrangement.
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 PackingHexagonal close packing has ABAB arrangement
Cubic close packing has ABCABC arrangement
There are 2 types of voids in 3 dimensional close packing- Tetrahedral and Octahedral voids.
Packing EfficiencyA Unit cell having lattice points only at the corners is called a simple unit cell
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.
Crystal LatticeNumber of atoms per unit cell in a simple cubic unit cell is 1
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 CellsDensity of a unit cell is the ratio of mass of the unit cell to its volume
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
Imperfections in CrystalsAny deviation from a perfectly ordered arrangement constitutes a defect or imperfection
Schottky defect is more common in ionic compounds with high coordination number
Frenkel defect is more common in ionic compounds with low coordination number