Solids have a specific shape because of the attractive forces between the particles of which they are composed.
Examples of different types of solids, the various particle (structural unit) types and the attractive forces between them are shown below.
Examples of different types of solids, the various particle (structural unit) types and the attractive forces between them are shown below.
As shown for the examples, the melting point of the solid depends on the strength of the attractive force between its particles (structural units).
| Type of solid | Particle type (structural unit) | Attractive force between particles (structural units) | |
| network | atoms | covalent bonds strong forces | Example: C(diamond) hard high melting |
| ionic | ions (cations and anions) | ionic bonds strong forces | Example: NaCl hard high melting |
| molecular | molecules | intermolecular attractive forces weak forces | Example: I2 soft low melting |
| metallic | atoms | metallic bonds moderate to strong forces | Example: Al usually hard and high-melting |