Nitrogen Fertilizer Identification

This question asks us to identify which of the given chemical compounds is not a nitrogen fertilizer. Nitrogen fertilizers are crucial for plant growth, providing essential nitrogen in a form that plants can absorb.

Analyzing the Options

Let's examine each option to determine its role as a fertilizer:

• Option 1: \((NH_4)_2SO_4\)
  This compound is known as ammonium sulfate. It is a common fertilizer because it contains nitrogen in the ammonium ion (\(NH_4^+\)) form, which plants can absorb. It also provides sulfur.
• Option 2: \(NH_4NO_3\)
  This is ammonium nitrate. It's a widely used fertilizer containing nitrogen in both ammonium (\(NH_4^+\)) and nitrate (\(NO_3^-\)) forms, both readily available for plant uptake.
• Option 3: \(N_2\)
  This represents elemental nitrogen gas. While nitrogen makes up about 78% of the Earth's atmosphere, the \(N_2\) molecule is very stable and unreactive. Most plants cannot directly utilize atmospheric nitrogen gas (\(N_2\)) for growth. Nitrogen fertilizers must contain nitrogen in a chemically fixed form (like ammonia or nitrate) that plants can absorb and metabolize. Therefore, \(N_2\) itself is not considered a nitrogen fertilizer.
• Option 4: \((NH_2)_2CO\)
  This is the chemical formula for urea. Urea is the most common nitrogen fertilizer globally. When applied to the soil, it is converted by soil microbes into ammonia and then nitrate, which plants can readily absorb.
• Option 5: (Empty Option)
  This option is empty and therefore does not represent a chemical compound or fertilizer.

Conclusion on Nitrogen Fertilizers

Based on the analysis, ammonium sulfate (\((NH_4)_2SO_4\)), ammonium nitrate (\(NH_4NO_3\)), and urea (\((NH_2)_2CO\)) all contain nitrogen in forms usable by plants and are therefore considered nitrogen fertilizers. Elemental nitrogen gas (\(N_2\)), although abundant, is not directly usable by plants and thus is not classified as a fertilizer.

The compound that is not a nitrogen fertilizer among the choices provided is \(N_2\).