Select the correct answer.
Looking across period 4 of the periodic table, potassium (atomic number 19) is followed by calcium (atomic number 20), which is followed by
scandium (atomic number 21). Which element should have the largest atomic radius?
Atomic radius refers to the distance between the nucleus of an atom to the outermost energy level.
The trend in atomic radius across a period is such that atomic radius decreases across the period from left to the right.
Decrease in atomic radius across the period is due to an increased nuclear charge.
Increased nuclear charge results from addition of protons which causes an increase in nuclear attraction to electrons as the number of energy levels remain constant.
Therefore, scandium will have the smallest atomic radius compared to calcium and potassium as it has more protons and thus a large nuclear charge.
