CuI (s) refers to solid copper iodide, which is a compound formed by the combination of copper ions (Cu⁺) and iodide ions (I⁻).
Copper ions (Cu⁺): These are positively charged particles that are formed when copper atoms lose electrons.
Iodide ions (I⁻): These are negatively charged particles that are formed when iodine atoms gain electrons.
Solid compound: A substance in which the constituent particles are tightly packed together in a fixed arrangement.