Final answer:
Arsenic, with an atomic number of 33, has five valence electrons, as indicated by its position in group 15 of the periodic table.
Step-by-step explanation:
The atomic number of arsenic (As) is 33, which means it has 33 protons and, when neutral, also 33 electrons. To determine the number of valence electrons arsenic possesses, we look at its position in the periodic table. Arsenic is in group 15, which typically means elements in this group have five valence electrons. Hence, arsenic has five valence electrons as well.
The electron configuration of arsenic can be represented as [Ar]3d¹104s²4p³, showing that there are five electrons in the outermost orbitals - two in the 4s subshell and three in the 4p subshell. These are the valence electrons that participate in chemical bonding.