Here's why:

* Properties of Metals: Metals are typically shiny, malleable (can be hammered into shapes), ductile (can be drawn into wires), good conductors of heat and electricity, and tend to lose electrons in chemical reactions.

* Properties of Nonmetals: Nonmetals are generally dull, brittle, poor conductors of heat and electricity, and tend to gain electrons in chemical reactions.

Sulfur powder fits the description of a nonmetal:

* Dull: Sulfur powder is yellow and not shiny.

* Brittle: It is easily broken into smaller pieces.

* Poor conductor: Sulfur is a poor conductor of heat and electricity.

Therefore, sulfur powder is classified as a nonmetal.