noun, masculine/aɾˈseniko/
arsénico is masculine in Spanish.
arsenic
Related: trióxido de arsénico
Borrowed from Latin arsenicum, from Ancient Greek ἀρσενικόν (arsenikón, “yellow arsenic”), identified by folk etymology with ἄρσην (ársēn, “male, manly”), but actually from Semitic source, and ultimately from an Avestan term meaning "gold". More at arsenic.