Here's why:

* Metalloids: Metalloids are elements that exhibit properties of both metals and nonmetals. They are located along the "staircase" line on the periodic table.

* Valence Electrons: Valence electrons are the electrons in the outermost shell of an atom, which are involved in chemical bonding.

* Boron's Electron Configuration: Boron has an atomic number of 5, meaning it has 5 electrons. Its electron configuration is 1s² 2s² 2p¹. The 2s² and 2p¹ electrons are in the outermost shell, giving Boron 3 valence electrons.