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Brittle Nature of Ionic Crystals

• Salt crystals are hard but brittle; they shatter under strong force (e.g., a hammer blow).

• Layers of ions shift relative to each other; like-charged ions repel, causing shattering.

Electrical Conductivity

• Solid sodium chloride does not conduct electricity; ions are not free to move within the crystal lattice.

• Ionic compounds conduct electricity when melted or dissolved in water:

  • Charged particles can move freely in a molten state or a solution, enabling conductivity.

• Properties used in ceramics for insulating high-voltage power lines.

Solubility of Ionic Compounds

• Solubility refers to how readily an ionic compound dissolves in water.

• Soluble ionic compounds disassociate in water; insoluble ionic compounds remain intact.

  • Depends on strength of attractions: ionic lattice forces vs. attraction to water molecules.

Properties of Ionic Compounds

• High melting points due to strong electrostatic attraction between ions (ex: sodium chloride at 801°C).

• Hard and brittle due to strong forces within the lattice; disrupt easily under stress.

• Used in bricks for furnaces and ceramic components for brake discs.

Ionic Bonding Model

• Ionic compounds form when metal atoms lose electrons (cations) and non-metal atoms gain electrons (anions).

• Lattice structure: cations and anions arranged to maximize electrostatic attractions.

• Example: Sodium Chloride (NaCl) has a 1:1 ratio of sodium to chloride ions.

Electron Transfer in Ionic Bonding

• Electron transfer diagrams show how ions are formed:

  • Sodium loses an electron to become Na⁺ (2,8) and chlorine gains an electron to become Cl⁻ (2,8,8).

Formation of Ionic Compounds

• Vigorous reactions occur between metals and non-metals to form ionic compounds.

• The octet rule describes the tendency of atoms to achieve stable electron configurations by losing or gaining electrons.

Naming Ionic Compounds

1. Cations are named after the metal.

2. Anions' names often end in '-ide' (ex: chloride)

3. Polyatomic anions may end in '-ate' or '-ite' depending on oxygen content.

Writing Chemical Formulas

• The formula of an ionic compound must balance the charges of its constituent ions.

• Use subscripts to indicate the number of each type of ion present (e.g., MgCl₂).

• Polyatomic ions are treated as single units in formulas.