Which statement best explains why calcium has a larger atomic radius than magnesium? a. calcium has a stronger nucleic charge than magnesium. b. calcium has elctrons in more energy levels than magnesium. c. calcium has more neutrons than magnesium. d. calciums third energy level contains more electrons than magnesiums.

Calcium has electrons in more energy levels than magnesium. The number of electron in calcium atom is 20 which means 4 energy levels. (2 electron in first shell+ 8 electron in second shell+8 electron in third shell+ 2 electron in fourth shell). While number of electron in magnesium atom is 12 which means 3 energy levels. (2 electron in first shell+ 8 electron in second shell+ 2 electron in third shell). Also the Calcium third energy level contains more electron than magnesium.