Noble gases: The elements in Group 0 of the periodic table (He, Ne, Ar, Kr, Xe, Rn) — unreactive gases with full outer electron shells.
Inert: Chemically unreactive — the old term for noble gases before their extreme stability was fully understood. "Noble" is the preferred modern term.
Full outer shell: When the outermost electron shell of an atom contains the maximum number of electrons (2 for helium in the 1st shell; 8 for neon, argon, etc. in higher shells). This configuration is associated with maximum stability and zero reactivity.
Monatomic: Existing as single, unbonded atoms. Noble gases are monatomic because their full outer shells mean they have no tendency to form bonds with other atoms.
This definitions covers Key Definitions within Group 0: Noble Gases for GCSE Chemistry. Revise Group 0: Noble Gases in Atomic Structure for GCSE Chemistry with 22 exam-style questions and 20 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 7 of 12 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Practice questions for Group 0: Noble Gases
Which group in the periodic table contains the noble gases?
Helium has only 2 electrons in its outer shell, yet it is still unreactive. Explain why.