Atoms of arsenic (as) are often added to silicon (si) in a process called doping to change the conductivity of the silicon. how does the addition of arsenic change the conductivity of silicon?

an atom of arsenic has one fewer valence electron and more electron shells than an atom of silicon, so the conductivity decreases because the arsenic atom gains an electron.
an atom of arsenic has one more valence electron and more electron shells than an atom of silicon, so the conductivity decreases because the arsenic atom loses the electron.
an atom of arsenic has one fewer valence electron and fewer electron shells than an atom of silicon, so the conductivity increases because the arsenic atom gains an electron.
an atom of arsenic has one more valence electron and more electron shells than an atom of silicon, so the conductivity increases because the arsenic atom loses the electron.