[PhyPharm] Solids and the Crystalline State

• Ionic Crystals

• Covalent Crystals

• Molecular Crystals

• Organic Crystals

• Metallic Crystals

Types of Crystals

Ions (e.g.Na+ and Cl- in NaCl)

Constituent Units of Ionic crystals

Molecules (e.g.CO2, Benzene, Chloroform, Naphthalene)

Constituent Units of Molecular Crystals

Atoms (e.g. Diamond, Graphite)

Constituent Units of Covalent Crystals

Aliphatic Hydrocarbons, Fatty acids

Constituent Units of Organic Crystals

Positive ions in electron gas

Constituent Unit of Metallic Crystals

Electrostatic attaraction

Bonding type of Ionic crystals

Covalent bonds

Bonding type of covalent crystals

Van Def Waals, Hydrogen Bonding

Bonding type of molecular crystals

Van Der Waals forces, Hydrogen bonding

Bonding type of organic crystals

Metallic bonding (delocalized electrons)

Bonding type of Metallic Crystals

Hard, Brittle, High melting points

Properties of Ionic and Covalent crystals

Soft, Low melting points

Properties of Molecular Crystals

Chain ends arranged parallel; fatty acid form layers or dimers

Properties of organic crystals

Good electrical conductors; hardness and melting point vary with lattice defects

Properties of Metallic Crystals

• Crystalline Solids

• Amorphous Solids

Types of Solids?

Highly ordered, Repeating 3D Lattice

Particle arrangement of Crystalline Solids

Random, Disordered arrangement

Particle Arrangement of Amorphous solids

Present

Long-range order of Crystalline Solids

Absent

Long-Range order of Amorphous solids

Sharp and well-defined

Melting point of Crystalline Solids

Gradual over a temperature range

Melting point of Amorphous Solids

Regular geometric forms (e.g. cubes, prisms)

Shape of Crystalline Solids

Irregular, No definite shape

Shape of Amorphous Solids

Breaks along specific planes

Cleavage of Crystalline Solids

Breaks irregularly

Cleavage of Amorphous solids

Yes (properties vary with direction)

Anisotropy of Crystalline Solids

No (Isotropic - same in all direction)

Anisotropy of Amorphous solids

Salt (NaCl, Quartz, Diamond)

Examples of Crystalline solids

Glass, Plastic, Rubber

Examples of Amorphous Solids

Electronics, Optics, Pharmaceuticals

Uses of Crystalline solids

Packaging, Lenses, Coating

Uses of Amorphous Solids

• One of the fundamental states of matter, alongside liquid, gas, and plasma

• Fixed shape and volume

• Particles are closely packed and vibrate in place

• Strong intermolecular forces keep particles in position

Crystal systems:

• Cubic (Sodium Chloride)

• Tetragonal (Urea)

• Hexagonal (Iodoform)

• Rhombohedral (Iodine)

• Monoclinic (Sucrose)

• Triclinis (Boric acid)

Crystals are classified into 6 distinct systems

Sodium Chloride

Cubic?

Urea

Tetragonal?

Iodoform

Hexagonal?

Iodine

Rhombohedral?

Sucrose

Monoclinic?

Boric acid

Triclinic?

X-rays are diffracted by crystals, similar to how visible light is dispersed by a ruled grating

What's the principle of X-ray diffraction in crystal structure analysis?

X-ray wavelengths are comparable to atomic/molecular distances in crystals

X-ray diffraction in crystal structure analysis, why it works?

Diffraction pattern is photographed on a sensitive plate placed behind the crystals

Method of X-ray diffraction in crystal structure analysis?

Uses reflection of x-rays from atomic planes to measure interplanar distances in the lattice

Modified technique of X-ray diffraction in Crystal structure analysis?

Determines crystals structure and atomic arrangement of various compounds

Applications of X-ray diffraction in Crystal Structure Analysis

Used when whole crystals are unavailable or unsuitable for analysis.

What is Powdered method in X-ray diffraction in crystal structure analysis?