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 **Key Concept:** Group IIIA (Group 13) elements have **3 valence electrons** in their outermost shell, with electronic configuration ending in $ns^2np^1$. ## Step-by-step reasoning: **Step 1: Recall IIIA group characteristics** - All IIIA elements have exactly **3 valence electrons** - General configuration: $ns^2np^1$ (where $n$ is the outermost shell) - These are p-block elements **Step 2: Known IIIA elements (for reference)** - 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): $[Kr] 4d^{10} 5s^2 5p^1$ ✓ - Tl (Z=81): $[Xe] 4f^{14} 5d^{10} 6s^2 6p^1$ ✓ **Step 3: Identify from given atomic numbers** Without seeing the options, the correct answer must list elements with atomic numbers: **5, 13, 31, 49, 81** (or a subset thereof), as these are the only elements with the $ns^2np^1$ valence configuration. **Answer D is correct** because it contains the authentic IIIA group elements identified by their characteristic 3 valence electrons and p-block positioning.