Question

1. which of the following elements has the largest atomic radius? sodium helium lithium potassium

Explanation:

Step1: Recall atomic - radius trend

Atomic radius decreases across a period and increases down a group in the periodic table.

Step2: Locate elements in periodic table

Helium (He) is in the first period, Group 18. Sodium (Na) is in the third period, Group 1. Lithium (Li) is in the second period, Group 1. Potassium (K) is in the fourth period, Group 1.

Step3: Compare atomic radii

Among these elements, potassium has the largest atomic number and is in the lowest - lying period among them. As we move down a group, the number of electron shells increases, leading to an increase in atomic radius. So potassium has the largest atomic radius among the given elements.

Answer:

C. Lithium