Silicon has 4 valence electrons, which are the electrons in the outermost shell. These are the electrons that participate in chemical reactions.

Here's why:

* Valence Electrons: Valence electrons are the ones most loosely held by the atom and are involved in forming chemical bonds.

* Silicon's Electronic Configuration: Silicon has the electronic configuration 1s²2s²2p⁶3s²3p². The 3s² and 3p² electrons are the valence electrons.

Therefore, the four valence electrons in silicon's outermost shell are the ones that take part in chemical reactions, including reactions with metals.