Of the known elements in the periodic table, how many are gases under normal atmospheric conditions?
Correct Answer: 11
Subject: chemistry
Explanation: • <b>Key Fact</b>
There are exactly 11 elements that exist as gases at normal temperature and pressure (NTP).
• <b>Supporting Detail</b>
These are H₂, N₂, O₂, F₂, Cl₂ (5 diatomic) and He, Ne, Ar, Kr, Xe, Rn (6 noble gases).
• <b>Related Concept</b>
Bromine and Mercury are the only two liquid elements at NTP.
• <b>Why wrong options are wrong</b>
Counts other than 11 miss or overcount the gaseous elements.
• <b>Exam Trick</b>
5 Diatomic + 6 Noble Gases = 11 Gaseous elements.
• <b>Additional Info</b>
All 11 gaseous elements are non-metals.