Question

select the correct answer. 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.

Explanation:

Step1: Recall atomic radius trend

Atomic radius decreases across a period.

Step2: Analyze elements

Potassium (K), calcium (Ca), scandium (Sc) are in period 4. K (atomic number 19) is first, then Ca (20), then Sc (21). As we move from left (K) to right (Sc) in period 4, atomic radius decreases. So K has the largest atomic radius.

Answer:

A. potassium