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 Group IIIA Elements **Group IIIA (Group 13) Characteristics:** - Valence electron configuration: $ns^2np^1$ - Three valence electrons in outermost shell - Forms +3 oxidation state typically **Step-by-step identification:** 1. **Recognize the pattern:** Group IIIA elements have **3 electrons in their valence shell** (2 in s-orbital, 1 in p-orbital) 2. **Eliminate non-IIIA elements:** - Groups IIA have $ns^2$ (2 valence e⁻) - Groups IVA have $ns^2np^2$ (4 valence e⁻) - Groups VA have $ns^2np^3$ (5 valence e⁻) - Transition metals have d-orbital electrons 3. **Known IIIA elements (by atomic number):** - B (5): $1s^2 2s^2 2p^1$ ✓ - Al (13): $[Ne] 3s^2 3p^1$ ✓ - Ga (31): $[Ar] 3d^{10} 4s^2 4p^1$ ✓ - In (49): $[Kr] 4d^{10} 5s^2 5p^1$ ✓ - Tl (81): $[Xe] 4f^{14} 5d^{10} 6s^2 6p^1$ ✓ **Answer D correctly lists all Group IIIA elements** by their atomic numbers, matching the $ns^2np^1$ valence configuration pattern.