Lead(II) iodide

Lead(II) iodide is a yellow crystalline ionic compound with formula PbI₂, composed of lead(II) cations and iodide anions. It is sparingly soluble in cold water and dissolves more readily in hot water.

Precipitation reaction: A chemical reaction in solution that produces an insoluble solid from dissolved substances. Mixing soluble lead and iodide salts forms solid PbI₂ by precipitation.
Lead(II) ion: The Pb²⁺ cation formed when a lead atom loses two electrons. Each formula unit of PbI₂ contains one lead(II) ion.
Golden rain experiment: A demonstration in which hot solutions of lead nitrate and potassium iodide produce shimmering yellow lead(II) iodide crystals upon cooling. The experiment makes PbI₂'s temperature-dependent solubility and vivid crystals visible.
Lead(II) bromide: An ionic compound with formula PbBr₂, composed of lead(II) and bromide ions. Replacing iodide with bromide changes the lead halide's color and physical properties.
Solubility equilibrium: The dynamic balance between a solid compound dissolving and its dissolved ions forming the solid. The equilibrium shifts with temperature, accounting for PbI₂'s greater solubility in hot water.
Iodide: The monatomic anion I⁻, formed when an iodine atom gains one electron. Two iodide ions balance the charge of each lead(II) ion in PbI₂.
Perovskite solar cell: A photovoltaic device that uses a perovskite-structured semiconductor to convert light into electricity. PbI₂ is used as a precursor in fabrication routes for lead-halide perovskite absorber layers.
Lead(II) chloride: An ionic compound with formula PbCl₂, composed of lead(II) and chloride ions. PbCl₂ is a closely related lead halide with different solubility and appearance.
Solubility product: An equilibrium constant describing the dissolution of a sparingly soluble ionic solid. The solubility product quantifies when dissolved lead and iodide ions precipitate as PbI₂.
Ionic bond: An electrostatic attraction between oppositely charged ions. Electrostatic attraction between Pb²⁺ and I⁻ ions holds the compound together.

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