Noble gases are typically unreactive because they have a full valence shell of electrons.

• A. Not true
• B. Sometimes true
• C. Often true
• D. True

Answer: (D)

A full valence shell makes an atom exceptionally stable, so it resists changing its electrons. Noble gases have complete outer electron shells (eight in most, helium with two), which means they have little tendency to gain, lose, or share electrons. That stability leads to high ionization energies and low electron affinities, so forming bonds is energetically unfavorable. As a result, noble gases are typically unreactive under normal conditions. There are exceptions under extreme conditions (for example, xenon can form a few compounds with fluorine), but those are rare and require special environments. So the statement is correct: their full valence shell is what mostly keeps them inert.