Without looking at the periodic table, select the elements of IIIA group of the periodic table (atom — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

# Solution: Identifying IIIA Group Elements **Understanding IIIA Group:** - IIIA (Group 13) elements have **3 valence electrons** in their outermost shell - Electronic configuration ends in: $ns^2np^1$ - Examples: B, Al, Ga, In, Tl **Method to Identify:** 1. **Write electron configurations** for given atomic numbers and check the outermost shell 2. **Look for the pattern** $ns^2np^1$: - B (Z=5): $1s^2 2s^2 2p^1$ ✓ - Al (Z=13): $1s^2 2s^2 2p^6 3s^2 3p^1$ ✓ - Ga (Z=31): $[Ar] 3d^{10} 4s^2 4p^1$ ✓ - In (Z=49): $[Kr] 4d^{10} 5s^2 5p^1$ ✓ 3. **Eliminate others**: - IIA (Group 2): $ns^2$ configuration - IVA (Group 14): $ns^2np^2$ configuration - VA (Group 15): $ns^2np^3$ configuration **Why D is correct:** Option D lists all elements with exactly **3 valence electrons** ($ns^2np^1$ configuration), which defines the IIIA/Group 13 family in the periodic table.