Final answer:
Arsenic has five valence electrons. These electrons are responsible for its chemical properties and make it a useful donor impurity in semiconductors.
Step-by-step explanation:
How many valence electrons does Arsenic have? Arsenic has five valence electrons. These electrons reside in the outermost energy level of an arsenic atom and are responsible for the chemical properties of the element. The electronic configuration of arsenic is [Ar]3dⁱ⁰ 4s² 4p³, which shows that there are five electrons outside of the noble gas core. The presence of these extra electrons in arsenic makes it useful as a donor impurity in semiconductor technology, where they contribute to electrical conductivity. Arsenic can exhibit different oxidation states, commonly +3 or +5, and even -3 in some arsenides.