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

• Atomicity of Primary Gases - Primary gases like oxygen (O₂), nitrogen (N₂), hydrogen (H₂), and others consist of molecules that are made up of two or more atoms of the same element. The atomicity of these primary gases depends on the type of molecule they form.
• For example:
  • Oxygen (O₂): The atomicity of oxygen in O₂ is 2 because it consists of two oxygen atoms.
  • Nitrogen (N₂): The atomicity of nitrogen in N₂ is 2 because it consists of two nitrogen atoms.
  • Hydrogen (H₂): The atomicity of hydrogen in H₂ is 2 because it consists of two hydrogen atoms.
  • Ozone (O₃): The atomicity of oxygen in ozone is 3 because it consists of three oxygen atoms. 

Explanation:

The atomicity of primary gases depends on how many atoms of the element are present in a molecule of that gas. For example, oxygen (O₂) has an atomicity of 2 because it consists of two oxygen atoms, nitrogen (N₂) has an atomicity of 2, hydrogen (H₂) has an atomicity of 2, and ozone (O₃) has an atomicity of 3 because it consists of three oxygen atoms.

Answer 2

Primary gases here refers to the common elemental gases like hydrogen, oxygen, and nitrogen, so checking how many atoms each of their molecules actually contains settles the atomicity.

1. 1: An atomicity of 1 would mean these gases exist as lone atoms, which is true only for noble gases like helium or argon, not for hydrogen, oxygen, or nitrogen, which are the primary gases being referred to.
2. 2: Hydrogen exists as H2, oxygen as O2, and nitrogen as N2, each made of exactly two atoms of the same element bonded together. Since all these common primary gases share this same diatomic structure, their shared atomicity is two.
3. 3: An atomicity of three matches ozone, O3, which is a special, less common, and less stable form of oxygen, not the primary diatomic gases being discussed.
4. 4: None of the primary gases, hydrogen, oxygen, or nitrogen, are known to bond four atoms of the same element together, so this option fits nothing here.

Since hydrogen, oxygen, and nitrogen all form two-atom molecules, the shared atomicity of these primary gases is two.

So the correct answer is 2.