Which is a gas at room temperature

Answer

At room temperature, Nitrogen (N$_2$) is a gas.

Below is a detailed explanation with chemical notations and equations:

Nitrogen (N$_2$)

Nitrogen, with the chemical symbol N, predominantly exists as a diatomic molecule in the atmosphere:

Nitrogen gas makes up approximately 78% of Earth's atmosphere. It is colorless, odorless, and exists in gaseous form at room temperature (around 20-25°C) and standard atmospheric pressure.

Confirmation of States of Other Elements

For clarity, let's also consider the states of the other elements at room temperature:

1. Aluminum (Al)

   • Aluminum is a solid metal.
   • It exhibits a metallic lattice structure.
   $$Al (s)$$

2. Potassium (K)

   • Potassium is an alkali metal and is solid at room temperature.
   • It has a body-centered cubic (bcc) crystalline structure.
   $$K (s)$$

3. Sodium (Na)

   • Sodium is another alkali metal that is also solid at room temperature.
   • Similar to potassium, it has a body-centered cubic (bcc) structure.
   $$Na (s)$$

Conclusion

Nitrogen (N$_2$) is the only element from the given list that is in a gaseous state at room temperature.

Understanding Gaseous State at Room Temperature

Substances in the gaseous state at room temperature are those that exist fully as gases under normal ambient conditions, usually defined as around 25°C (298 K) and 1 atmosphere of pressure. Several factors determine whether a substance will be in the gaseous state, such as intermolecular forces and molecular weight.

Key Factors

Intermolecular Forces

Intermolecular forces significantly influence the state of matter. In gases, these forces are weaker compared to solids and liquids, allowing molecules to move freely.

• Van der Waals forces
• Dipole-dipole interactions
• Hydrogen bonding

Molecular Weight and Structure

Lighter molecules tend to be gases because they have higher kinetic energy at a given temperature, which makes it easier for them to overcome intermolecular forces.

Ideal Gas Law

The behavior of gases can be understood using the Ideal Gas Law, given by:

Where:

• $P$ is the pressure,
• $V$ is the volume,
• $n$ is the number of moles,
• $R$ is the universal gas constant,
• $T$ is the temperature in Kelvin.

Common Gases at Room Temperature

1. Hydrogen (H$_2$)
2. Oxygen (O$_2$)
3. Nitrogen (N$_2$)
4. Carbon Dioxide (CO$_2$)
5. Noble gases (e.g., Helium (He), Neon (Ne), Argon (Ar))

These substances predominantly exist in the gaseous state due to their low boiling points and weak intermolecular attractions.

Phase Diagrams

A phase diagram helps illustrate the conditions under which a substance exists in different states. For gases, the relevant portion typically shows the substance as a gas at room temperature and standard pressure.

Example Calculation

To determine the number of moles of an ideal gas under standard conditions, given the volume is $22.4 \, L$:

Conclusion

Substances in the gaseous state at room temperature share characteristics like weak intermolecular forces and low molecular weight. The Ideal Gas Law and phase diagrams are essential tools for understanding and predicting the behavior of these gases under various conditions.

Atmospheric Composition of Earth

The Earth's atmosphere is a complex mixture of various gases, each contributing to different processes that sustain life and the environment. This mix of gases is what makes Earth's climate and weather systems work.

Primary Gases

The main components of Earth's atmosphere are:

• Nitrogen (N$_2$): Constitutes about 78.08%
• Oxygen (O$_2$): Makes up roughly 20.95%
• Argon (Ar): Accounts for about 0.93%

These gases make up the bulk of the atmosphere. The small percentage of Carbon Dioxide (CO$_2$), around 0.04%, is critical for processes such as photosynthesis.

Trace Gases

In addition to the primary gases, the atmosphere contains trace amounts of other gases such as:

• Neon (Ne)
• Helium (He)
• Methane (CH$_4$)
• Krypton (Kr)
• Hydrogen (H$_2$)

While these gases are present in very small quantities, they play significant roles in various atmospheric processes.

Atmospheric Layers

The Earth's atmosphere is divided into several layers, each with its own distinct characteristics:

1. Troposphere: The lowest layer, where weather phenomena occur.
2. Stratosphere: Contains the ozone layer, which protects living organisms from harmful solar UV radiation.
3. Mesosphere: Meteors burn up in this layer.
4. Thermosphere: Contains the ionosphere, which is important for radio communication.
5. Exosphere: The outermost layer, where atmospheric particles are sparse.

Equations Representing Atmospheric Composition

The following LaTeX formulas represent the fractional composition of the primary gases:

Human Impact

Human activities have significantly altered the atmospheric composition, particularly through the increase of greenhouse gases such as CO$_2$ and methane (CH$_4$). Understanding and maintaining the balance of these gases is crucial for combating climate change and protecting life on Earth.