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SOLIDS - Coggle Diagram
SOLIDS
Types of solids
Molecular solids: made of molecules, soft, low melting points.
Covalent network solids: made of atoms connected by covalent bonds, very hard, high melting points.
Ionic solids: made of positive and negative ions, hard, brittle, high melting points.
Metallic solids: made of metal atoms, positive ions in a sea of delocalized electrons, good conductors.
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Energy
The crystalline state is more stable than the amorphous state because it has lower Gibbs Free Energy (ΔG). Amorphous solids have higher ΔG, so they can slowly transform into crystalline solids, though the reverse process is energetically unfavorable. This transformation is rare because the high viscosity of amorphous solids greatly slows molecular movement.
Crystallization
Crystallization occurs from melts, solutions, or vapors under conditions of supersaturation or super-cooling. Crystallization happens more easily when structural units are symmetrical and held by weaker forces metals crystallize easily, while silicates form amorphous solids when cooled. In polymers, only linear and regular macromolecules can partly crystallize because of their size and strong intermolecular forces, they usually contain both crystalline and amorphous regions.
Unit Cells
A crystalline solid has a well-ordered, repeating arrangement of atoms, ions, or molecules. This repeating pattern forms a structure called a crystal lattice, made up of unit cells, which are the smallest repeating units that retain the symmetry of the entire crystal. The three-dimensional packing of these unit cells creates the overall crystal structure.
Types
Cubic: All sides equal, axes at right angles
Tetragonal: Two sides equal, one different; axes at right angles
Hexagonal: Three equal axes at 120°, one perpendicular and different in length
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Monoclinic: Three unequal axes, two at right angles, one inclined
Triclinic: Three unequal axes, all at oblique angles.