On the periodic table, it is in the same family as silver and gold.
This element violates the Madelung rule by having ten electrons in the 3d orbital. Speculum metal is composed of tin and this element. The sulfate of this element is commonly used along with steel wool to demonstrate exothermic reactions. On the periodic table, it is in the same family as silver and gold. When exposed to air, it can form a green patina known as verdigris. For 10 points, name this element with symbol Cu.
This element violates the Madelung rule by having ten electrons in the 3d orbital.
{copper} [accept {Cu} before mentioned]