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

Potassium should have largest atomic radius.......

'cause on moving to right, attractive force between nucleus and electrons increases and causes shielding effect, due to which atomic radius get smaller

Answer 2

Answer: Potassium amongst the given elements have the largest atomic radius.

Explanation:

Atomic radius of an atom is defined as the distance between the nucleus and the outermost orbital of the atom containing electrons.

Atomic radius decreases across the period because as the atomic number increases, there is an addition of electron to the orbital and nucleus more strongly attract that electron towards itself and results in the shrinking of the atom.

Hence, the atomic size or atomic radius decreases across the period.

The given elements are the elements which belong to the same period which is period 4. Therefore the order of atomic radius follows the order:

K > Ca > Sc

Hence, potassium has the largest atomic radius from the given elements.