Calcium sulfide

Calcium sulfide (CaS) is an ionic compound composed of calcium cations and sulfide anions. It is a solid that reacts with water and acids, releasing hydrogen sulfide under suitable conditions.

Rock-salt crystal structure: A cubic crystal structure in which each ion is surrounded by six oppositely charged ions. Calcium sulfide commonly adopts this arrangement, with calcium and sulfide ions alternating through the lattice.
Phosphor: A material that emits light after absorbing energy from an external source. Doped calcium sulfide has served as a host material for luminescent phosphors.
Calcium: A reactive alkaline-earth metal with atomic number 20, commonly forming Ca²⁺ ions. Calcium supplies the doubly charged cation in calcium sulfide.
Oldhamite: A rare calcium sulfide mineral found chiefly in meteorites and some terrestrial deposits. Oldhamite is the naturally occurring mineral form of calcium sulfide.
Ionic bond: An electrostatic attraction between oppositely charged ions formed through electron transfer. Calcium transfers two electrons to sulfur, producing the ions that bind in CaS.
Cathodoluminescence: Light emitted by a material when it is excited by an electron beam. Calcium sulfide phosphors can emit visible light under electron-beam excitation.
Sulfur: A nonmetallic chemical element with atomic number 16 that forms sulfide ions in ionic compounds. Sulfur gains two electrons to become the sulfide component of CaS.
Meteorite: A fragment of extraterrestrial material that survives passage through Earth’s atmosphere and reaches the ground. Calcium sulfide occurs as oldhamite in some meteorites, especially enstatite-rich examples.
Hydrolysis: A chemical reaction in which a substance is cleaved or transformed by water. Moisture can convert calcium sulfide into calcium-containing products while releasing hydrogen sulfide.
Luminous paint: A coating formulated to emit visible light after excitation or through radioactive energy transfer. Calcium sulfide was used in early glow-in-the-dark paints before more stable phosphors became common.

Linked from 2 pages

Barium sulfideCompared with: CaS is a neighboring Group 2 sulfide with different solubility and industrial behavior.