Understanding Ozone and Allotropes

The question asks about the nature of Ozone. Let's examine the properties of Ozone ($\text{O}_3$) and compare them with the options provided.

What is Ozone?

Ozone is a molecule made up of three oxygen atoms chemically bonded together. Its chemical formula is $\text{O}_3$. It is a pale blue gas with a distinct pungent smell. It is found in the Earth's atmosphere, particularly in the stratosphere, where it forms the ozone layer which absorbs most of the Sun's ultraviolet (UV) radiation.

What are Allotropes?

Allotropes are different structural modifications of an element. This means that an element can exist in more than one form in the same physical state, with the atoms arranged in different ways. These different forms have different physical properties.

For example, carbon exists as diamond, graphite, fullerenes, etc., which are all allotropes of carbon.

Is Ozone an Allotrope of Oxygen?

Oxygen is an element. The most common form of oxygen we breathe is diatomic oxygen, which consists of molecules containing two oxygen atoms ($\text{O}_2$). Ozone ($\text{O}_3$) is another form of oxygen, made of three oxygen atoms.

Both $\text{O}_2$ and $\text{O}_3$ are made solely of oxygen atoms. They are different forms of the same element (oxygen) existing in the gaseous state, but with different molecular structures (diatomic vs. triatomic). Therefore, Ozone is an allotrope of oxygen.

Analyzing the Options:

1. a cyclic molecule: Ozone has a bent structure, not a cyclic one. The three oxygen atoms form a bent chain.
2. an allotrope of oxygen: As discussed above, Ozone ($\text{O}_3$) is a different form of the element oxygen than the common oxygen ($\text{O}_2$). Both exist in the same physical state (gas) but have different structures and properties. Thus, Ozone is an allotrope of oxygen.
3. a compound of oxygen: A compound is formed when two or more different elements combine chemically. Ozone is made only of oxygen atoms; there are no other elements present. Therefore, Ozone is not a compound of oxygen. It is an elemental form.
4. is as stable as oxygen: Ozone is significantly less stable than diatomic oxygen ($\text{O}_2$). Ozone readily decomposes into oxygen gas ($\text{O}_2$). For example: $\text{2O}_3 \rightarrow \text{3O}_2$. This decomposition is exothermic and can be explosive under certain conditions.

Based on the analysis, Ozone is an allotrope of oxygen.