Here's why:
* Block elements are classified based on the electron configuration of their outermost electrons.
* Titanium (Ti), Aluminum (Al), and Zinc (Zn) are all transition metals. They belong to the d-block because their valence electrons occupy the d orbitals.
* Vanadium (V) is also a transition metal, but it has an anomalous electron configuration. It's expected to have the configuration [Ar] 3d4 4s2, but instead has [Ar] 3d5 4s1. This deviation means it's considered a d-block element, not a block element.
Therefore, Vanadium is the only element in the list that isn't strictly classified as a block element due to its unique electron configuration.
