Correct Answer: Neon
Subject: 2025
Explanation: <p><strong>Key Fact:</strong> Neon (symbol $Ne$, atomic number 10) is a noble gas located in Group 18 of the periodic table.</p><p><strong>Additional Info:</strong> Noble gases (Helium, Neon, Argon, Krypton, Xenon, Radon) have completely filled outer electron valence shells (octet rule: $2, 8$ for Neon), making them exceptionally stable and chemically unreactive under standard conditions. Neon glows with a reddish-orange light in high-voltage electrical discharge signs.</p><p><strong>Why the other options are wrong:</strong> Oxygen is a Group 16 chalcogen; Fluorine is a Group 17 halogen; Nitrogen belongs to Group 15 pnictogens.</p><p><strong>Exam Trick:</strong> Group 18 inert gases = He, Ne, Ar, Kr, Xe, Rn.</p><p><strong>Final Answer:</strong> Neon</p>