Mineralogy — Definition Check In mineral classification, “phosphates” are the group of minerals in which one or more metallic elements are chemically combined with the phosphate anion (PO4). Fill the blank to complete the definition correctly.

Introduction / Context:
Minerals are grouped by their dominant anion or anionic group, which strongly controls crystal structure and chemical behavior. Recognizing these families (silicates, carbonates, oxides, phosphates, etc.) helps in field identification, laboratory classification, and understanding geologic environments of formation.

Given Data / Assumptions:

• The prompt asks for the correct completion of a standard mineralogical definition.
• Phosphate minerals are characterized by the phosphate anion group, commonly written as PO4.
• Metal cations (such as Ca, Fe, Al) bond with the phosphate group to form distinct minerals (for example, apatite).

Concept / Approach:
In Dana/Strunz-style classification, mineral classes are keyed to their principal anion. Phosphates contain the PO4 group; carbonates contain CO3; silicates contain SiO4; oxides are simple O^2- combinations without a complex anion group like PO4 or CO3. Therefore, to finish the statement “chemically associated with the phosphate compound ____,” the logically correct word is “phosphates.”

Step-by-Step Solution:

Verification / Alternative check:
Compare with other classes: carbonates (CO3), oxides (O), silicates (SiO4). Only phosphates are built around the PO4 group, confirming the choice.

Why Other Options Are Wrong:

• oxides: Do not contain the phosphate group; dominated by O^2- bonding.
• silicates: Built on SiO4 tetrahedra, not PO4.
• carbonates: Characterized by CO3, not PO4.

Common Pitfalls:
Confusing mineral names ending in “-ite” (a naming convention) with mineral classes. Always check the dominant anion to determine the class.

Final Answer:
phosphates