An element X which is a yellow solid at room temperature shows catenation and allotropy. X forms two oxides which are also formed during the thermal decomposition of ferrous sulphate crystals and are the major air pollutants.
Identify the element X.

Explanation

To identify the element X based on the given clues, we can follow these steps:

### Step 1: Analyze the properties of element X
- The element X is described as a yellow solid at room temperature.
- It shows catenation and allotropy.

### Step 2: Understand catenation and allotropy
- Catenation refers to the ability of an element to form chains or rings of atoms.
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