Which of these elements on the Periodic Table is a Noble Gas?

The story behind the answer

Neon is a noble gas (Group 18) with a full valence shell, making it extremely stable and mostly unreactive. That “inert” nature is the hallmark of noble gases. By contrast, iodine is a halogen (very reactive), potassium is an alkali metal (highly reactive), and cobalt is a transition metal.

Fun context: Neon glows a distinctive reddish-orange in discharge tubes—hence “neon lights.” Memory tip: Most noble gases end in “-on” (Neon, Argon, Krypton, Xenon, Radon; Helium is the exception). Or use the mnemonic: “He Never Argues; Kings Xenially Relax” (Helium, Neon, Argon, Krypton, Xenon, Radon).