Question

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?

Answer 1

Atomic radius decreases across a row (increasing positive charge in the nucleus causes electrons in the same energy level to "shrink" into the nucleus due to electrostatic attraction). This means that potassium has the largest atomic radius in period 4.

(Hope I am right xd)