Give below are two statements:
Statement - I: Noble gases have very high boiling points.
Statement - II: Noble gases are monoatomic gases. They are held together by strong dispersion forces. Because of this they are liquefied at very low temperature. Hence, they have very high boiling points.
In the light of the above statements, choose the correct answer from the options given below:

Solution

Chemistry ma’am · 4 steps

Weak dispersion forces mean low boiling points, and both statements get exactly this backwards.

1. What holds them. Noble gases are monoatomic, so the only attraction between their atoms is the London dispersion force. For such small, non-polar atoms this force is very weak.
2. Check Statement I. Weak forces need very little energy to overcome, so noble gases boil at very low temperatures. Helium boils at about 4 K, and even radon, the heaviest, boils at only about 211 K. Statement I is false.
3. Check Statement II. The word "monoatomic" is correct, but the forces are weak, not strong. The statement also contradicts itself: a gas that liquefies only at very low temperature has a low boiling point, not a high one. Statement II is false.
4. So. Both statements are false, so the answer is (a).

The idea to keep. For noble gases, test every claim against one fact: single atoms held only by weak dispersion forces. That gives low boiling points, which rise down the group as the atoms get bigger and more polarisable.

Answer from the NTA final answer key. Solution by PrepWiser.