The elements with the same number of energy levels are the ones that belong to the same period of the periodic table.
Copper and Zinc both belong to the 4th period of the periodic table.
Nickel belongs to the 4th period and palladium to the 5th period.
Lithium belongs to the 2nd period and Magnesium to the 3rd period.
It means that the correct answer is Copper and Zinc, they belong to the same period,
