Arsenic is a metallic element. Iron is a transition element. Barium has an oxidation number of minus one. Most of the elements on the periodic table are nonmetals.
Sodium is more active than potassium.
Chlorine is more active than iodine. The d sublevel has 10 orbitals. A normal copper atom has twenty five electrons. A mercury atom has five electron energy levels. There are thirty five neutrons in a chlorine atom.