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Solids: Introduction

Crystal Types

Fig.1
Overview

Solids are classified into various categories (crystal lattice) according to the nature of the repetitive units (motifs) that make up the crystal and the bonds between them. However, this classification cannot be considered a sharp delineation of individual types. Instead, within most crystals there are transitions between the different types, just as there are transitions between bond types as well.

Metallic crystals
Metallic crystals consist of a regular arrangement of metal cations with delocalized electrons that hold the crystal together (Abb. 2) .
Ionic crystals
Ionic crystals consist of cations and anions. The interactions stem from ionic attraction (Abb. 3) .
Atomic crystals
Atomic crystals (covalent crystals) consist of atoms linked by covalent bonds (Abb. 4) .
Molecular crystals
Molecular crystals consist of separate molecules held together by dipole forces. Crystals of the noble gases may be considered a special case as their atoms will form crystal lattices held together by induced dipoles at low temperatures (Abb. 5) .

Figures

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Fig.2
Metallic crystal

An arbitrary metal

Note: Click on the picture for an animated illustration.

Fig.3
Ionic crystal

NaCl

Fig.4
Atomic crystal

Diamond, C

Fig.5
Molecular crystal

Hexagonal ice

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