Question

1. which of the following elements has the largest atomic radius? calcium sodium potassium magnesium

Explanation:

Step1: Recall atomic - radius trend

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

Step2: Locate elements in periodic table

Calcium (Ca) is in Group 2, Period 4; Sodium (Na) is in Group 1, Period 3; Potassium (K) is in Group 1, Period 4; Magnesium (Mg) is in Group 2, Period 3.

Step3: Compare atomic radii

Since K and Ca are in Period 4 and Na and Mg are in Period 3, atoms in Period 4 are larger than those in Period 3. Among K and Ca, K is in Group 1 and Ca is in Group 2. As we move from left - to - right across a period, atomic radius decreases. So K has a larger atomic radius than Ca.

Answer:

Potassium