Question: why are arsenic and antimony chemically similar?
Answer: Arsenic has a noble gas configuration of [Ar] 4s2 3d10 4p3, for a total of 5 valence electrons. Antimony has a noble gas configuration of [Kr] 5s2 4d10 5p3, for a total of 5 valence electrons. ... Because these two elements have the same number of valence electrons, they have similar chemical behavior.