Flashcards for NEET Chemistry - The Solid State

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Chemistry

The Solid State

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The Solid State

Crystalline

Solids

Long-range order

Sharp melting point

Anisotropic

Definite enthalpy of fusion

e.g. Sodium chloride and quartz

Amorphous Solids

Short-range order

Soften over a range of temperature

Pseudo solids or super cooled liquids

Isotropic

e.g. Quartz, glass, rubber, plastics

Non-polar Molecular Solids

Soft and non-conductors of electricity

The atoms or molecules are held by weak dispersion forces or London forces

Low melting points and are usually in the liquid or gaseous state at room temperature

e.g. H₂, Cl₂, CCl₄, and I₂

Polar Molecular Solids

Soft and non-conductors of electricity

The atoms or molecules are held by dipole-dipole interactions

Low melting points and are usually in the liquid or gaseous state at room temperature

e.g. Solid SO₂, HCl, NH₃

Hydrogen-Bonded Molecular Solids

Non-conductors of electricity

Molecules are held by hydrogen bonds

Generally, they are volatile liquids or soft solids under room temperature

e.g. H₂O (ice)

Ionic Solids

Electrical insulators in the solid state but conduct electricity in the molten state

Cations and anions bound by strong electrostatic forces

High melting and boiling points

Hard and brittle

e.g. NaCl, MgO, ZnS, CaF₂

Metallic Solids

Positive ions surrounded by a sea of free electrons

Show high electrical and thermal conductivity

Lustrous, malleable and ductile

e.g. Fe, Cu, Ag, Mg

Covalent Solids

Network Solids or giant molecules

Hard and brittle

Insulators and non-conductors of electricity (graphite-exception)

Extremely high melting points and may even decompose before melting

e.g. Quartz, diamond, graphite

Cubic Crystal System

Primitive, Body-centred, Face-centred

Axial distances or edge lengths – a = b = c

Axial angles – α = β = γ = 90°

Examples – NaCl, Zinc blende, Cu

Tetragonal Crystal System

Primitive, Body-centred

Axial distances or edge lengths – a = b ≠ c

Axial angles – α = β = γ = 90°

Examples – White tin, SnO₂, TiO₂, CaSO₄

Orthorhombic Crystal System

Primitive, Body-centred, Face-centred, End-centred

Axial distances or edge lengths – a ≠ b ≠ c

Axial angles – α = β = γ = 90°

Examples – Rhombic sulphur, KNO₃, BaSO₄

Hexagonal Crystal System

Primitive

Axial distances or edge lengths – a = b ≠ c

Axial angles – α = β = 90°, γ = 120°

Examples – Graphite, ZnO, CdS

Rhombohedral or Trigonal Crystal System

Primitive

Axial distances or edge lengths – a = b = c

Axial angles – α = β = γ ≠ 90°

Examples – Calcite (CaCO3), HgS (cinnabar)

Monoclinic Crystal System

Primitive, End-centred

Axial distances or edge lengths – a ≠ b ≠ c

Axial angles – α = γ = 90°, β ≠ 90°

Examples – Monoclinic sulphur, Na₂SO₄.10H₂O

Triclinic Crystal System

Primitive

Axial distances or edge lengths – a ≠ b ≠ c

Axial angles – α ≠ β ≠ γ ≠ 90°

Examples – K₂Cr₂O₇, CuSO₄.5H₂O, H₃BO₃

Primitive Cubic Unit Cell

Atoms are present only at its corner

Total number of atoms in one unit cell is = 1 atom

Body-centred Cubic (bcc) Unit Cell

An atom at all the corners and also one atom at its body centre

Total number of atoms in one unit cell is = 2 atoms

Face-centred Cubic (fcc) Unit Cell

Atoms at all the corners and at the centre of all the faces of the cube

Total number of atoms in one unit cell is = 4 atoms

Frenkel Defect

Also called dislocation defect

Ionic substances, having a large difference in the size of ions

The smaller ion (usually cation) is dislocated

e.g. ZnS, AgCl, AgBr and AgI due to the small size of Zn²⁺ and Ag⁺ ions

Schottky Defect

Ionic substances having a similar size of ions

The number of missing cations and anions are equal

e.g. NaCl, KCl, CsCl and AgBr

Semiconductors

Solids with conductivities in the intermediate range from 10^–6 to 10⁴ ohm^–1m^–1

Electrical conductivity increases with a rise in temperature

Intrinsic semiconductors – Si and Ge

n-Type Semiconductor

Intrinsic semiconductor (Si and Ge) doped with an electron-rich impurity, i.e. group 15 elements

P, As or Sb

p-Type Semiconductor

Intrinsic semiconductor (Si and Ge) doped with an electron-deficit impurity, i.e. group 13 elements like B, Al or Ga

Paramagnetism

Due to the presence of one or more unpaired electrons

Weakly attracted by a magnetic field

Lose their magnetism in the absence of a magnetic field

E.g. O₂, Cu²⁺, Fe³⁺, Cr³⁺

Diamagnetism

All the electrons are paired

Weakly repelled by a magnetic field

e.g. H₂O, NaCl and C₆H₆

Ferromagnetism

Attracted very strongly by a magnetic field

Can be permanently magnetised

e.g. iron, cobalt, nickel, gadolinium and CrO₂

Antiferromagnetism

Domains are oppositely oriented and cancel out each other’s magnetic moment

e.g. MnO

Ferrimagnetism

Weakly attracted by the magnetic field

Lose ferrimagnetism on heating and become paramagnetic

e.g. Fe₃O₄ (magnetite) and ferrite like MgFe₂O₄ and ZnFe₂O₄

Also check:

• NEET Chemistry Syllabus
• NEET Chemistry Important Topics
• NEET Chemistry MCQs
• How to Score 160 Plus in NEET Chemistry