The identity of a subshell is determined by the azimuthal quantum number ($l$). For $l = 3$, the subshell corresponds to an f-subshell (specifically 4f since $n=4$).

The maximum number of electrons a subshell can accommodate is given by the formula: $\text{Max Electrons} = 2(2l + 1)$

Substituting $l = 3$: $\text{Max Electrons} = 2(2 \times 3 + 1) = 2(7) = 14$

This principle explains why the Lanthanoid and Actinoid series (f-block elements) consist of 14 elements each, as the f-orbitals are being filled .