Question

The largest atomic radius among the following is:

• A. Helium
• B. Carbon
• C. Oxygen
• D. Potassium

Answer 1

The correct option is D

Potassium

Explanation for correct option

(D) Potassium

Periodic trend of atomic radius

• An element's atomic radius decreases across a period from left to right.
• An element's atomic radius increases from top to bottom in a group in the periodic table.

Largest radius

• Helium is an element with the atomic number 2 that belongs to the group 18 and period 1 of the periodic table.
• Carbon is an atomic number 6 element that belongs to group 14 and period 2 of the periodic table.
• Oxygen is an atomic number 8 element that belongs to the group 16 and period 2 of the periodic table.
• Potassium is an atomic number 19 element that belongs to group 1 and period 4 of the periodic table.
• The atomic radius increases down the group and decreases along the period.
• As a result, potassium has the largest atomic radius.

Explanation for incorrect options

• Potassium has the largest atomic radius among the elements. Hence all other options (A), (B) and (C) are incorrect.

Therefore, the correct option is (D) Potassium.