Which of the following pair of elements belong to the same period? — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Step 1: Identify the periods of the elements in each option. Step 2: Mg (period 3), Sb (period 5); Ca (period 4), Zn (period 4); Na (period 3), Ca (period 4); Ca (period 4), Cl (period 3). Step 3: Thus, Calcium (Z=20) and Zinc (Z=30) both belong to the fourth period, matching option (b).