Nitrogen

Nitrogen is a non-metallic element found in Group 15 of the periodic table. It is a colourless, tasteless, and odourless gas that makes up about 80% of the Earth's atmosphere. Nitrogen is essential for all living organisms. The chemical symbol for nitrogen is N.

1.0What Is Nitrogen?

Nitrogen is a nonmetallic element in the periodic table's pnictogens group, positioned between carbon and oxygen. It plays a key role in forming amino acids and is a fundamental component of all living tissues. As a constituent of DNA, nitrogen is crucial for genetic coding, making it an essential element of life. It has five electrons in its outer shell, making most of its compounds trivalent.

Nitrogen is found in nitrates and nitrites in soil and water, which are interconnected and part of the nitrogen cycle. Industrial processes release nitrogen extensively, leading to increased nitrite and nitrate content in the soil and water through reactions in the nitrogen cycle.

• Physical State: Colorless, odourless gas; can also exist as a liquid.
• Molecular Form: Found as N₂
• Electron Configuration: 1s² 2s² 2p³.

2.0Anomalous Properties of Nitrogen

The following unique properties distinguish nitrogen from other elements in its group, affecting its chemical behaviour and bonding.

• Small Size and High Electronegativity: Nitrogen is smaller and has a higher electronegativity than other group members.
• High Ionisation Enthalpy: Nitrogen has a higher ionisation enthalpy.
• Lack of d Orbitals: Unlike heavier group members, Nitrogen does not have available d orbitals.
• pπ-pπ Multiple Bonds: Nitrogen can form pπ-pπ multiple bonds with itself and other small, highly electronegative elements (e.g., C, O).
• Diatomic Molecule: Exists as a diatomic molecule (N_2​) with a triple bond, leading to a high bond enthalpy (941.4 kJ mol^–1).
• Single Bond Weakness: The single N–N bond is weaker than the single P–P bond due to the high interelectronic repulsion caused by the small bond length, which results in a weaker catenation tendency.
• Covalency Limitation: The absence of d orbitals limits nitrogen's covalency to four.
• No dπ-pπ Bonds: Unlike heavier elements, nitrogen cannot form dπ-pπ bonds (e.g., R₃​P=O or R_3​P=CH₂​).
• No dπ-dπ Bonds: Phosphorus and arsenic can form dπ-dπ bonds with transition metals, but nitrogen cannot due to the absence of d orbitals.

3.0Dinitrogen

Dinitrogen (N₂) is a colourless, odourless, tasteless, and non-toxic gas. It exists primarily in N₂ and has two stable isotopes, ¹⁴N and ¹⁵N. With very low solubility in water, dinitrogen is highly inert at room temperature due to the strong triple bond (N≡N) that requires significant energy to break. Its reactivity increases with temperature, enabling it to react with metals to form nitrides and hydrogen to form ammonia in the Haber process.

Read More: Dinitrogen

4.0Compounds of Nitrogen

Nitrogen forms various compounds, including ammonia, nitrous oxides, and cyanides. Azides, either inorganic or organic nitrogen compounds, consist of three nitrogen atoms within the group (N₃​). Nitrogen compounds are often produced through a chemical reaction called nitration, which occurs when nitric acid reacts with organic compounds.

• Ammonia (NH₃​)

Ammonia is a colourless gas with a pungent odour. Its freezing point is 198.4 K, and its boiling point is 239.7 K. Similar to water, Ammonia molecules are associated with hydrogen bonds in solid and liquid states. Ammonia gas is thoroughly soluble in water, producing an aqueous solution called ammonium hydroxide (NH_4​OH).

• Oxides Of Nitrogen: 

Nitrogen Oxides are gases composed of nitrogen and oxygen. 

Nitrous Oxide (N₂O), Nitric Oxide (NO), Nitrogen Dioxide (NO₂​), Dinitrogen Pentoxide (N_2​O_5​)

• Nitrogen Oxoacids

Nitrogen forms several oxoacids, including hyponitrous acid (H₂N₂O_2​), nitrous acid (HNO_2​), and nitric acid (HNO₃), the most significant of which is nitric acid (HNO₃).

Nitric acid is a colourless liquid with a freezing point of 231.4 K and a boiling point of 355.6 K. Laboratory-grade nitric acid typically contains about 68% HNO3_33​ by mass and has a specific gravity of 1.504 g/ml.

• Ammonium Nitrate (NH₄NO₃)
• Sodium Nitrate (NaNO₃)
• Sodium Nitrite (NaNO₂)

5.0Uses of Nitrogen

• Ammonia Production: Nitrogen is used to produce ammonia, which is then converted into nitric acid for fertilisers.
• Fertilisers and Explosives: Nitric acid salts such as potassium nitrate, ammonium nitrate, and nitroglycerin are common in fertilisers and explosives.
• Refrigeration: Liquid nitrogen is used to freeze food, preserve biological materials, and maintain biological samples in cryogenic conditions. 
• Construction: Compressed nitrogen gas enhances power in the hydraulic systems of construction equipment, such as hydraulic hammers.
• Airbags: Nitrogen gas is generated from sodium azide to inflate airbags.
• Soil and Water: Nitrogen is present in soil and water as nitrates and nitrites and is integral to the nitrogen cycle.
• Inert Atmosphere: Nitrogen gas is used for inert gas asphyxiation and to create an inert atmosphere where oxygen might cause fires, explosions, or oxidation hazards.