Nitrogen Dioxide

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Created by: Team Chemistry -, Last Updated: April 27, 2024

Nitrogen Dioxide

Nitrogen dioxide, often symbolized as NO₂,s a fascinating molecular compound in the field of chemistry. Nitrogen dioxide is a gas that’s both intriguing and vital to understand, especially for young science enthusiasts. Picture this: a reddish-brown gas with a sharp, acrid smell, playing a significant role in our planet’s atmosphere and our daily lives. NO₂ comes from various sources, including car engines, power plants, and even from lightning during thunderstorms. It’s a part of a bigger family of gases called nitrogen oxides, which are not only key players in forming smog and acid rain but also contribute to the nutrient cycle within ecosystems. Knowing about nitrogen dioxide helps us grasp the delicate balance of our environment and the impact human activities have on it. This gas teaches us the importance of clean air and the steps we need to take to protect our planet.

What is Nitrogen Dioxide?

Nitrogen dioxide is a gas that’s a bit of a troublemaker in our air. It’s made up of nitrogen and oxygen, two elements that are usually harmless on their own. But when they come together to form nitrogen dioxide, they create a reddish-brown gas that can make our air dirty and unhealthy to breathe. Cars, trucks, and factories release a lot of this gas when they burn fuel, which is why you might see or smell it more in big cities or near busy roads. It’s important to keep an eye on nitrogen dioxide because it can irritate our lungs and make it harder for us to breathe, especially for people with asthma or other lung conditions.

Chemical Names and Formulas

NameNitrogen dioxide
IUPAC NameNitrogen dioxide
Alternate Namesnitrito, nitro, nitrogen oxide

Structure of Nitrogen Dioxide


Nitrogen dioxide, often symbolized as NO2, is like a tiny molecule puzzle with one nitrogen atom holding hands with two oxygen atoms. Imagine the nitrogen atom in the center, acting as a hub, and the two oxygen atoms on either side, kind of like a V-shape. This arrangement is not just random; it’s because of the way electrons, the tiny particles that orbit atoms, like to share space and bond together. This sharing creates a strong connection between the nitrogen and oxygen, making NO2 a stable, yet reactive, molecule in our environment. What makes nitrogen dioxide really interesting is that it has an odd number of electrons, which means it’s always looking to share or steal an electron from other molecules, leading to various chemical reactions, especially in our atmosphere. This tiny molecular structure, small but mighty, plays a big role in the chemistry of the air we breathe.

Preparation of Nitrogen Dioxide

Creating nitrogen dioxide (NO₂) can seem like a bit of chemistry magic, but it’s actually based on simple reactions. One common way to make NO₂ is by reacting copper with nitric acid. When these two substances meet, they undergo a chemical reaction that releases nitrogen dioxide as a gas. The equation for this reaction looks something like this

3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 4H₂O + 2NO₂

In simple terms, three pieces of copper react with eight units of nitric acid to produce copper nitrate, water, and our main event, nitrogen dioxide gas. This process is a great example of how combining different elements and compounds can create something entirely new. It’s important to note that making nitrogen dioxide should only be done in a controlled, safe laboratory environment because NO2 is a potent gas that can be harmful to breathe. This process highlights the fascinating ways in which chemicals react to form new substances, showing the dynamic nature of chemistry.

Physical Properties of Nitrogen Dioxide

AppearanceReddish-brown gas that can give the air a hazy look.
SmellHas a sharp, biting odor that’s pretty distinct.
State at Room TemperatureGas form, making it blend into the air we breathe.
Solubility in WaterSlightly soluble, meaning it can mix into water a bit, but not completely.
DensityHeavier than air, which means it tends to hang low to the ground.
Melting PointTurns from gas to liquid at about -11.2°C (11.84°F).
Boiling PointBecomes a liquid at 21.15°C (70.07°F) under atmospheric pressure.

Chemical Properties Of Nitrogen Dioxide

Reacts with Water

When NO₂ encounters water, it doesn’t just dissolve; it actively reacts to form nitric acid (HNO₃) and nitrogen monoxide (NO). This reaction is a critical component of acid rain formation. The reaction can be represented by the chemical equation: 3CO₂ + 2H₂O → 2HNO₃ + NO.

Forms Dinitrogen Tetroxide

NO₂ can join with another NO₂ molecule to create dinitrogen tetroxide (N₂O₄), especially at lower temperatures or under pressure. This behavior is reversible, showing how NO₂ can exist in two forms, balancing between them based on the environment. This equilibrium is illustrated by: 2NO₂ ⇌ N₂O₄

Acts as an Oxidizing Agent

As a potent oxidizing agent, NO₂ can steal electrons from other substances. This property makes it a critical player in combustion reactions, smog formation, and various atmospheric processes. Its role as an oxidizer highlights NO₂’s contribution to environmental pollution and chemical transformations in the atmosphere.

Absorbs UV Light

NO₂ has the ability to absorb ultraviolet (UV) light from the sun, influencing atmospheric chemistry and affecting Earth’s climate and air quality. This absorption is essential for understanding the balance of energy in our atmosphere and the impacts of pollutants on global warming and weather patterns.

Nitrogen Dioxide (NO₂) Chemical Compound Information

Chemical Identifiers

CAS Registry Number10102-44-0
PubChem Compound ID3032552
PubChem Substance ID24857797
SMILES IdentifierN(=O)[O]
InChI IdentifierInChI=1/NO2/c2-1-3
RTECS NumberQW9800000
MDL NumberMFCD00085341

NFPA label

NFPA Health Rating3
NFPA Fire Rating0
NFPA Reactivity Rating0
NFPA HazardsOxidizing Agent

Uses of Nitrogen Dioxide


Making Nitric Acid

One of the most important uses of NO is in producing nitric acid (HNO₃), a key ingredient in fertilizers and explosives. By reacting NO₂ with water, manufacturers create this powerful acid, fueling agricultural growth and various industrial processes.

Precursor for Chemicals

NO₂ is crucial in the chemical industry as a precursor to many other chemicals. Its reactive nature makes it perfect for synthesizing a wide range of compounds, including plastics, dyes, and pharmaceuticals, showcasing its versatility in manufacturing.

Rocket Fuel

In the aerospace field, NO₂ serves as an oxidizer for rocket fuels. Its ability to help burn fuel more efficiently makes it invaluable for launching spacecraft, highlighting its role in exploration beyond Earth.

Controlling Pollution

Surprisingly, NO₂ also has a role in reducing pollution. It’s used in scrubbing systems to remove harmful pollutants from industrial exhaust gases, turning it from a pollutant into a pollution fighter.

Analyzing the Atmosphere

Scientists use NO₂ to study and monitor the Earth’s atmosphere. Its presence helps researchers understand air quality, ozone formation, and the dynamics of climate change, making it a key indicator in environmental science.

Food Coloring

NO₂ indirectly contributes to food coloring production. It’s involved in creating specific dyes that color our foods, demonstrating its unexpected role in the food industry.

Side Effects Of Nitrogen Dioxide

Health Concerns: Breathing in NO2 can be harmful, especially for people with asthma or lung conditions. It can irritate the airways, making it harder to breathe and increasing the risk of respiratory infections. This is why clean air is so important for our health.

Environmental Impact: NO2 doesn’t just stop at affecting our health; it also plays a role in forming smog and acid rain. Smog can reduce visibility and harm wildlife, while acid rain can damage forests, lakes, and buildings. NO2’s ability to absorb sunlight also contributes to the warming of the Earth’s atmosphere, adding to climate change challenges.

Ozone Layer: Closer to the ground, NO2 can help form ground-level ozone, a key component of urban smog. However, this isn’t good for us or the environment, as it can lead to breathing problems, harm plants, and reduce crop yields.


Is Nitrogen Dioxide Harmful to Health?

Yes, nitrogen dioxide can irritate the respiratory system, exacerbate asthma, and reduce lung function, making it harmful, especially to those with respiratory conditions.

What is the Main Source of Nitrogen Dioxide?

The primary source of nitrogen dioxide is the burning of fossil fuels by vehicles, power plants, and industrial facilities, contributing to air pollution.

Does Nitrogen Dioxide Pollute the Air?

Absolutely, nitrogen dioxide is a significant air pollutant that contributes to smog, acid rain, and the greenhouse effect, impacting air quality and health.

What Causes NO2 in House?

Indoor NO2 can come from gas stoves, heaters, and tobacco smoke, accumulating in poorly ventilated homes and impacting indoor air quality.

How Do You Remove Nitrogen Dioxide from Indoor Air?

Improving ventilation, using air purifiers with HEPA filters, and reducing the use of gas-burning appliances can effectively lower NO2 levels indoors.

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