Question

Atomicity of primary gases is:

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

Diatomic molecules, such as O\(_2\) and N\(_2\), have an atomicity of 2.

Answer 1

The Correct Option is B

Step 1: Concept.
The common primary gases, hydrogen (H2), oxygen (O2), and nitrogen (N2), all exist as two atoms of the same element bonded together.

Step 2: Read off the atomicity.
Since each of these molecules carries exactly two atoms, and this pattern holds across all three primary gases, their atomicity is two.

Step 3: Final Answer.
The atomicity of primary gases is 2.

Answer 2

Each wrong option actually matches some other gas, just not the primary ones being asked about here, so ruling those out by name clears up the answer.

1. 1: This atomicity belongs to noble gases such as helium or neon, which exist as single unbonded atoms. These are not the primary gases, hydrogen, oxygen, nitrogen, that the question means.
2. 3: This atomicity belongs to ozone specifically, a special triatomic form of oxygen, not the ordinary diatomic oxygen gas or the other primary gases.
3. 4: No standard elemental gas among hydrogen, oxygen, or nitrogen bonds four atoms together, so this number does not correspond to any of the primary gases.
4. 2: Ruling out the noble-gas case and the ozone case and the unmatched case leaves two, which is exactly the atomicity shared by H2, O2, and N2, the actual primary gases in question.

Since 1 belongs to noble gases and 3 belongs to ozone specifically, and 4 matches nothing, only 2 correctly describes hydrogen, oxygen, and nitrogen.

So the correct answer is 2.