Advanced Placement (AP) Chemistry Practice Exam

Brass is classified as a substitutional alloy. In substitutional alloys, the atoms of the alloying elements replace some of the atoms in the host metal lattice. In the case of brass, it is primarily composed of copper and zinc. The sizes of the copper and zinc atoms are similar enough that zinc atoms can effectively replace some copper atoms in the metallic lattice structure without disrupting the overall arrangement significantly. This substitution of one metal for another affects the properties of the alloy, giving brass characteristics such as improved corrosion resistance, workability, and a pleasing appearance, making it useful for various applications, including in musical instruments, hardware, and decorative items.

This distinction from other options is important to understand. For example, interstitial alloys occur when smaller atoms fit into the spaces (interstices) between larger metal atoms, which is not the case in brass as both components are of comparable size. Neither covalent nor ionic compounds represent metallic alloys; they involve different types of bonding and structures that do not align with the properties or composition of brass.