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?

A.
potassium

B.
calcium

C.
scandium

D.
All three have the same atomic radius.

Answer 1

A. potassium

Step-by-step explanation:

Potassium is expected to have the greater atomic radius from the given choices of element.

Atomic radius is taken as half of the inter-nuclear distance between two covalently bonded atoms of non-metallic elements or half of the distance between two nuclei in the solid states of metals.

• Across a period, the atomic radii decreases progressively from left to right.
• This is due to the progressive increase in the nuclear charge without increase in the number of electronic shells.