Ionic solids: structure, bonding and properties

Ionic Solids:

• TYPE OF PARTICLE: Ions.
• Ionic solids are made of positive and negative ions held together in a 3D lattice.
• ATTRACTIVE FORCE: Ionic bonding.
• Ionic solids are held together by the strong electrostatic attraction (ionic bonding) between oppositely charged ions.

MELTING POINT:

• - Ionic solids have high melting points as a large amount of energy is needed to break the strong ionic bonds between oppositely charged ions.
• *Note* At room temperature nearly all ionic substances are solids

Deformation of the Solid:

• Ionic solids are extremely brittle due to the nature of the lattice.
• Distortion of the lattice causes ions of the same charge to align and the strong electrostatic repulsion between the two like charges causes the lattice to fracture.
• Therefore solids are not malleable to ductile.

Vocab/Definitions:

• Brittle: Hard but liable to break easily. Synonym: Breakable
• Ductile: able to be drawn out into a thin wire., able to be deformed without losing toughness; pliable, not brittle.. Synonym: flexiable, bendy.
• Malleable: able to be hammered or pressed into shape without breaking or cracking. Synonym: Ductile.
• Soluble: able to be dissolved, especially in water.

Solubility:

• Many ionic solids are soluble in water (a polar solvent) due to attractive forces from polar of water molecules.
• Eg: NaCl dissolves in water. The strong attraction between the polar water molecules and the charged ions overcomes the ionic bonds. Polar water molecules pull ions from the lattice resulting in the solid dissolving
• Ionic solids are usually insoluble in non-polar solvents (e.g. hexane) as the non-polar molecules cannot exert a force to overcome the ionic bonds.

Conductivity:

• Ionic solids do not conduct electricity. Charged particles (ions) are present however in order for them to conduct electricity they need to be free moving, as they are held together in a fixed position in the in the lattice, THEY ARE NOT FREE MOVING
• However if the ionic solid is in melted, or dissolved in water, the ions will be free to move, and the liquid will conduct electricity.