# What is the electron configuration for As_3?

Do you mean $\text{arsenide ion, } A {s}^{3 -}$?
Reduction of the Group 15 elements can lead to to ${N}^{3 -} ,$ ${P}^{3 -}$, and $A {s}^{3 -}$ ions. In this configuration the atom has the same electronic configuration as the nearest Noble Gas.
For $\text{arsenic}$, this is $\text{krypton, } Z = 36$.