Final answer:
Silicon is the element from the options given that is classified as a metalloid. Metalloids have properties that are a mix between metals and nonmetals and are positioned along the periodic table's stair-step line.
Step-by-step explanation:
Among the options provided, Silicon is classified as a metalloid. Metalloids have properties that are intermediate between those of metals and nonmetals, and they are typically located along the stair-step line of the periodic table. To illustrate, sodium (Na) is a metal, oxygen (O) is a nonmetal, and gold (Au) is also a metal. Silicon (Si), on the other hand, is a well-known metalloid, widely used in electronics due to its semiconductor properties.
Boron, arsenic, and antimony are additional examples of metalloids, each with diverse uses in different fields, such as technology and materials science. Silicon is especially prominent in the tech industry for its use in making semiconductor devices, which are essential components in computers and other electronic gadgets.