Question

why are noble gases generally unreactive? they have a high atomic mass; they tend to lose electrons easily; their outer electron shell is full; they are highly reactive nonmetals

Explanation:

To determine why noble gases are unreactive, we analyze each option:

• "They have a high atomic mass": Atomic mass doesn't determine reactivity; e.g., radon has high mass but is noble (unreactive), so this is incorrect.
• "They tend to lose electrons easily": Noble gases don't lose electrons easily; they have stable electron configurations, so this is wrong.
• "Their outer electron shell is full": Noble gases have a full valence (outer) electron shell, giving them stability and low reactivity, which matches their properties.
• "They are highly reactive nonmetals": Noble gases are unreactive, so this contradicts their nature.

Answer:

Green box: Their outer electron shell is full