Solid State Chemistry - Lecture 1 (JEE 2027)

Vocabulary flashcards based on the VMC ONLINE Solid States Class-1 lecture covering classification, properties, and structural units of solids.

Properties of Solid State

Characterized by stronger interparticle forces, shorter interparticle distance, lower thermal energy, fixed positions where particles oscillate about their mean position, and definite mass, volume, and shape.

Crystalline solid

A true solid with regular geometrical ordered arrangement of particles, long-range order, sharp melting point, characteristic enthalpy change of fusion, and cleavage property resulting in smooth surfaces.

Amorphous solid

A pseudo solid or supercooled liquid with no regular geometrical ordered arrangement of particles, short-range order, no sharp melting point, and no cleavage property (irregular surfaces).

Anisotropic

A characteristic of crystalline solids where physical properties like mechanical strength, electrical conductivity, and refractive index have different values when measured along different directions.

Isotropic

A characteristic of amorphous solids where physical property values remain the same when measured along different directions.

Polycrystalline solid

Solids that appear amorphous but possess a microcrystalline structure, such as metals.

Polymorphism

When a substance has the same chemical composition but different structures of solid form, such as Carbon appearing as Diamond, Graphite, or Fullerene.

Isomorphism

When different chemical compositions result in the same structure of solid form.

Metallic solid

A solid consisting of kernels (nucleus + inner shells) and valence electrons (mobile/delocalized electrons) held together by metallic bonds.

Covalent/Network solid

A solid form of non-metallic elements like $B_{(s)}$, $C_{(s)}$, or $Si_{(s)}$ where atoms are linked by strong, directional covalent bonds into a network.

Ionic solid

A hard and brittle solid composed of cations and anions held by electrostatic forces; it acts as an insulator in solid form but a conductor in liquid and aqueous forms.

Non-polar molecular solid

Soft solids with low melting points held by dispersion forces, such as $Ar_{(s)}$, $CH_{4(s)}$, $CO_{2(s)}$, and $C_{60(s)}$.

Polar molecular solid

Soft solids with low melting points held by dipole-dipole forces, such as $SO_{2(s)}$ and $HCl_{(s)}$.

H-bonded molecular solid

Solids such as $H_2O_{(s)}$ (Ice) and $CH_3COOH_{(s)}$ held by hydrogen bonding; they can be hard and exist in liquid or solid form at room temperature.

Inorganic graphite

Boron Nitride ($BN$).

Inorganic benzene

Borazole ($B_3N_3H_6$).

Lattice point/Lattice site

The position in space occupied by a single constituent particle (atom, ion, or molecule) of a solid.

Space lattice

An ordered arrangement of infinite lattice points in space where the environment at each point is similar.

Unit cell

The smallest repeating unit of lattice points in space that can generate the whole lattice upon translational displacement.

Unit cell parameters

The dimensions and angles that define the cell: line ($a$), parallelogram ($a, b, \theta$), or parallelepiped (a, b, c, \text{ and } \text{\alpha, \beta, \gamma}).