Understanding the Concept:
The aggregation number ($N_{\text{agg}}$) is defined as the average number of surfactant monomers clustered together within a single organized micelle structure once the Critical Micelle Concentration (CMC) is exceeded.
Structural Demarcation:
• When surfactants assemble into simple, thermodynamically favored spherical micelles, the size of the core is constrained by the length of the fully extended hydrophobic tail of the monomer.
• Geometric constraints dictate that for traditional low-molecular-weight amphiphilic agents in aqueous media, a spherical topology can typically hold between 50 to 100 monomers without creating a core vacuum or forcing headgroups too close together.
• Aggregation numbers significantly above 100 generally force structural transitions into non-spherical geometries, such as cylindrical, ellipsoidal, or lamellar bilayer configurations, to optimize thermodynamic stability.
Hence, option (B) represents the standard range for simple spherical micelles.