Which of the following elements is in the same period as phosphorus? A. CarbonB. Magnesium C. NitrogenD. Oxygen

Magnesium. (B.)

Period is the horizontal row in the periodic table

The answer is B

Explanation:

Elements in the periodic table are arranged according to there atomic numbers in groups (vertical columns) and periods (horizontal rows). Elements having the same number of valence electrons are in the same group in the periodic table while elements in the same period have the same number of electron shells.

Phosphorus has 3 electron shells, hence the right element in the options provided must have 3 electron shells in order to be in the same period with phosphorus.

Carbon has 2 electron shells hence it is found in period 2 Magnesium has 3 electron shells hence it is found in period 3 Nitrogen has 2 electron shells hence it is found in period 2 Oxygen has 2 electron shells hence it is found in period 2

From the above, we can deduce that magnesium is found in the same period (period 3) with phosphorus.