Malleability refers to the ability of a material to deform under compressive stress, often characterized by the material's ability to form a thin sheet. In the solid state, malleability is generally associated with metals.
Among the options provided:
- Phosphorus (P) is a nonmetal and is known to be brittle.
- Strontium (Sr) is an alkaline earth metal and has reasonable malleability.
- Antimony (Sb) is a metalloid and, while somewhat malleable, is also more brittle than metals.
- Copper (Cu) is a highly malleable metal.
Given this understanding, phosphorus (P) would be the least malleable in its solid state, as it is a nonmetal and does not exhibit malleability like metals do.