Determine the identity of an element that has completely filled the first, second, and third shells and has three electrons in the fourth shell. Is it a metal or a nonmetal? In which orbital is the last electron found?

• A. The element is zinc which is a metal. Its last electron can be found in the 4s-orbital.
• B. The element is gallium which is a metal. Its last electron can be found in the 4p-orbital.
• C. The element is copper which is a metal. Its last electron can be found in the 4s-orbital.
• D. The element is bromine which is a nonmetal. Its last electron can be found in the 4p-orbital.

Answer: (B)