MINERAL GROUPS — Chemical basis of phosphates Phosphates are minerals where one or more metallic elements are chemically associated with which phosphate group (write the correct chemical unit)?

Introduction / Context:
Minerals are classified by their dominant anion or anionic group. The phosphate class includes economically significant minerals like apatite that are vital for fertilizers and geochemical cycles.

Given Data / Assumptions:

• The task is to identify the chemical group defining phosphates.
• We focus on the fundamental anionic unit rather than oxidation states or full mineral formulas.
• Charge is implicit; exam keys often present the group without the superscript charge.

Concept / Approach:
The phosphate anion is built from phosphorus and oxygen as tetrahedral PO4 units (formal anion PO4^3−). Mineral structures incorporate this group with various cations (e.g., Ca in apatite Ca5(PO4)3(F,Cl,OH)).

Step-by-Step Solution:
Recall defining anionic group for phosphates → PO4.Eliminate other species (PO3, PO2, PO) which correspond to different stoichiometries or do not define the phosphate mineral class.Note that P2O5 is an oxide formula used in chemical analysis, not the anionic group in crystal structures.

Verification / Alternative check:
Reference mineralogy shows the phosphate group present as discrete tetrahedra linked by cations; apatite is the archetype.

Why Other Options Are Wrong:
PO3/PO2/PO — incorrect stoichiometries for the phosphate group.P2O5 — oxide representation of phosphorus pentoxide; not the anion unit in phosphate minerals.

Common Pitfalls:
Mixing analytical oxide notation (e.g., %P2O5) with structural anionic groups (PO4).

Final Answer:
PO4