The elements that have 3 electrons in their outermost shell are in Group 13 (or IIIA) of the periodic table. These are:

* Boron (B)

* Aluminum (Al)

* Gallium (Ga)

* Indium (In)

* Thallium (Tl)

These elements are known as the boron group or triels. They have a common electron configuration of ns² np¹, where n is the principal quantum number.