Question

In spite of having positive charge on the ions `H_3O^+` as well as `NH_4^+`, why are they not considered as electrophiles?

Answer 1

Because they cannot directly bond to a nucleophile, due to having no vacant orbitals.

---

An electrophile must be able to directly bond to a nucleophile by accepting an electron pair.

In `"NH"_4^(+)` and `"H"_3"O"^(+)`, the electrophile is `"H"^(+)`, and not the entire ions themselves.