Answer: They have completely filled valence shells with high Zeff.
- A They have completely filled valence shells with high Zeff
- B They have unusually large atomic radii compared to their period
- C They possess very few electrons in their outer shell
- D They are inherently radioactive elements
Correct answer: A. They have completely filled valence shells with high Zeff
Explanation: Noble gases have fully filled valence shells and the highest Zeff in their period, requiring maximum energy to ionise.
The complete modern periodic table (118 elements). Image: Cepheus et al., Public Domain, via Wikimedia Commons.
Concept context
The periodic table organises all 118 elements by atomic number and similar properties. Study periodic trends like atomic radius, ionization energy, and electronegativity, and learn how an element's position predicts its behaviour.
Read the full Classification of Elements and Periodicity in Properties notes →