Anirudh Walia is teaching live on Unacademy Plus
Solid State Anirudh Walia
About me B.Tech (final year) Mechanical Engineering, VIT Vellore Follow me on Unacademy at: Course fees : CONTRIBUTE (optional) Rate , review, recommend or share the lessons. https://unacademy.com/user/anirudhw28 e Doubt/feedback/query in comment section.
Course Targeted for Class XII Jee Advanced , Jee Main etc. AIIMS, NEET etc.
Lesson 1 Topics covered e Classification of solids Unit cells and its types
Solids Solids are the chemical substances which are characterised by define shape and volume, rigidity, high density, low compressibility. The constituent particles (atoms, molecules or ions) are closely packed and held together by strong interparticle forces Types of Solids The solids are of two types: Crystalline solids and Amorphous solids.
S.No Crystalline solid Amorphous solids These doesn't have any regular arrangement of the constituent particles in space Theseare super cooled liquids or pseudo soilds. These have short order arrangement of particle. These have definite and regular arrangement of the constituent particles in space. 2 These are true solids. 3 These have long order arrangement of the particles. These are anisotropic in nature, i.e, their physical These are isotropic in nature i.e., their physical properties are different in different directions. propeties are same in all the directions. 5 They have sharp melting points. 6 They undergo a clean cleavage when cut. They melt over a certain range of temperature. They undergo irregular cleavage when cut.
Type of Solid Intermolecular forcesProperties Examples Ionic Brittle, hard high MeltingNaCI, KCI, MgCl2 lon-Ion forces Dispersion /H-bond Soft, low melting non- Molecular forces/Dipole-Dipole conducting Hard: High melting point conducting Covalent network Covalent bonds C-Diamond SiO2 Variable hardness and meltingNa, Zn, Cu, Fe ness and meltin Metallic Metallic bonds
Unit cell e The smallest geometrical portion of the crystal lattice which can be used as repetitive unit to build up the whole crystal is called unit cell
Types of Unit Cell (i) Simple or primitive Unit cell: In which the particles are present at the corners only. Fig. 1.8: In a simple cubic unit cell. each corner atom is shared between 8 unit cells.
In al, since each cubic unit cel has 8 atoms on its corners. the total number of corners, the total nunm atoms in one unit cell is 8 -= 1 atom. 8