Helium

Helium, lighter than air and second only to hydrogen in the universe, is not just for balloons! This comprehensive guide delves into Helium’s fascinating journey from the Big Bang to high-tech industries today. Teachers, equip yourself with engaging examples and understand how Helium floats above the rest in both chemical uniqueness and practical application. Enhance your lessons with the science of Helium, its safe use, and its critical role in research and technology.

What is Helium?

Helium – A noble gas with the chemical symbol He and atomic number 2, Helium is renowned for its inertness and lighter-than-air properties. It’s the second most abundant element in the universe, primarily formed through nuclear fusion in stars. In its earthly applications, Helium is critical in various fields, from scientific research and medical technologies to party balloons and deep-sea diving. Its low boiling point and non-reactivity make it indispensable in cryogenics and as a protective atmosphere for arc welding. Helium is a cornerstone in understanding the universe’s workings and a vital tool in modern technology.

Other Noble Gases

Neon

Argon

Krypton

Xenon

Radon

Helium Formula

• Formula: He
• Composition: A single atom of helium.
• Bond Type: Helium atoms do not typically form bonds due to their full valence shell.
• Molecular Structure: Monatomic gas.
• Electron Configuration: Two electrons in the outermost shell, making it highly stable and inert.
• Significance: Essential in cryogenics and as a cooling medium, helium is also used in balloons and as an inert gas shield in welding.
• Role in Chemistry: Used as a non-reactive carrier gas in gas chromatography and as a protective atmosphere in various applications due to its inertness.

Atomic Structure of Helium

Properties of Helium

Physical Properties of Helium

Property	Description
Atomic Number	2
State at Room Temperature	Colorless, odorless, and tasteless gas.
Boiling Point	Very low at -268.93°C (-452.07°F), close to absolute zero.
Density	Very light, about 0.1786 grams per liter at STP.
Solubility	Practically insoluble in water.
Speed of Sound	Approximately 3 times faster in helium than in air.
Specific Heat	High specific heat, especially at constant volume.
Thermal Conductivity	Excellent conductor of heat, superior to all gases except hydrogen.

Chemical Properties of Helium

1. Inertness: Helium is extremely inert and does not react with other elements or compounds under normal conditions. This is due to its filled valence shell (1s²).
   • No known stable compounds at standard conditions.
2. Non-flammability: Helium does not burn nor support combustion, making it safe for use in various applications including as a protective atmosphere.
3. Atomic Size and Electron Configuration: Helium has the smallest atomic radius of all elements because its nucleus is tightly bound, and it has only two electrons.
   • Electron Configuration: 1s2
4. Ionization Energy: Helium has the highest first ionization energy of all the elements because removing an electron disrupts its stable, filled electron shell.
   • First Ionization Energy: $24.5874\text{eV}$
5. Reactivity and Formation of Compounds: Due to its complete electron shell, Helium typically does not form compounds. Some high-pressure and exotic compounds have been observed, but these are not stable under normal conditions.
   • Examples include molecules like HeNe or ions in extreme conditions but none stable at room temperature or natural environments.
6. Occurrence in Nature: While Helium is the second most abundant element in the universe, primarily formed through nuclear fusion in stars, it is relatively rare on Earth and is usually extracted from natural gas reserves.
   • In the universe: $\text{He}$ is mostly produced in stars through the proton-proton chain reaction and the carbon-nitrogen-oxygen cycle.

Helium’s chemical properties are dominated by its lack of reactivity, which stems from its complete valence electron shell, making it uniquely suitable for a wide variety of applications, especially where non-reactivity is required. Its physical properties, such as low boiling point and high thermal conductivity, make it ideal for cryogenics and other specialized uses.

Thermodynamic Properties of Helium

Property	Value
Atomic Number	2
Atomic Weight	4.002602 g/mol
Phase at Room Temperature	Gas
Density	0.1786 g/L (at 0°C, 1 atm)
Boiling Point	-268.93°C (-452.07°F)
Melting Point	-272.20°C (-457.96°F) at 2.5 MPa
Specific Heat Capacity (Cp)	5.193 J/(mol·K) at 25°C
Thermal Conductivity	0.1513 W/(m·K) at 300K
Critical Temperature	-267.96°C (-450.33°F)
Critical Pressure	0.22746 MPa

Electromagnetic Properties of Helium

Property	Value
Electronegativity (Pauling scale)	Essentially 0 (Helium is a noble gas)
Ionization Energy	First: 2372.3 kJ/mol, Second: 5250.5 kJ/mol
Refractive Index	1.000035 (at 0°C, 101.325 kPa for λ=589.3 nm)

Atomic Properties of Helium

Property	Value
Atomic Number	2
Atomic Weight	4.002602 g/mol
Electron Configuration	1s²
Covalent Radius	28 pm
Van der Waals Radius	140 pm
Ionization Energies	First: 2372.3 kJ/mol, Second: 5250.5 kJ/mol

Nuclear Properties of Helium

Property	Value
Isotopes	Helium-3 (³He), Helium-4 (⁴He)
Natural Abundance	³He: trace, ⁴He: 99.99986%
Nuclear Spin	³He: 1/2, ⁴He: 0
Magnetic Moment	³He: -2.12762 nuclear magnetons
Stable Isotopes	⁴He
Radioactive Isotopes	³He (stable in terrestrial conditions but considered a primordial nuclide)

Chemical Compounds of Helium

Helium is unique among the elements due to its extreme chemical inertness. As a noble gas with a completely filled valence electron shell, it doesn’t naturally form chemical compounds under standard conditions. However, under extreme conditions, such as very high pressures or in the presence of plasma, it can form exotic compounds. Here are six noteworthy compounds involving helium, although it’s important to note that these are not typically encountered in everyday chemistry:

1. Helium Hydride (HeH⁺)
   • Equation: He+H⁺→HeH⁺
   • Conditions: Formed in high-energy environments like the interstellar medium.
2. Helium-Nitrogen Compound (HeN)
   • Equation: He+N₂→HeN
   • Conditions: Created in plasma conditions, not stable under normal conditions.
3. Helium-Neon Compound (HeNe)
   • Equation: He+Ne→HeNe
   • Conditions: Observed under specific laboratory conditions, primarily in laser technology.
4. Helium Compound with Fluorine (HeF)
   • Equation: He+F₂→HeF
   • Conditions: Requires extreme conditions, such as in a plasma state.
5. Helium Dimer (He₂)
   • Equation: 2He→He₂​
   • Conditions: Occurs at very low temperatures and high pressures, often considered a van der Waals molecule.
6. Helium Oxide (HeO)
   • Equation: He+O₂→HeO
   • Conditions: Forms only under extreme laboratory conditions, not a stable compound in normal environments.

Isotopes of Helium

Isotope	Atomic Mass	Natural Abundance	Stability	Description
Helium-3 (³He)	3	Very Rare (~0.0001%)	Stable	Less abundant isotope with one neutron. Used in cryogenics, as a neutron detector, and potential fuel for nuclear fusion.
Helium-4 (⁴He)	4	Abundant (~99.9999%)	Stable	Most common isotope with two neutrons. Formed in alpha decay of heavier elements and used in cryogenics, as a lifting gas, and in gas chromatography.

Uses of Helium

1. Cryogenics: Due to its low boiling point, helium is used as a coolant in cryogenics, particularly for cooling superconducting magnets in MRI machines and other scientific equipment.
2. Lifting Gas: Helium is lighter than air and non-flammable, making it the safer choice over hydrogen for inflating balloons, airships, and blimps.
3. Gas Chromatography: As an inert gas, helium is used as a carrier in gas chromatography, ensuring substances are efficiently and safely separated and analyzed.
4. Pressurizing and Purging: In space technology and high-pressure systems, helium is used for pressurizing fuel tanks and purging systems, thanks to its inertness and low density.
5. Welding: Helium is used as a shielding gas in arc welding, protecting the weld area from atmospheric gases that might corrupt the weld.
6. Breathing Mixtures: For deep-sea diving, helium is mixed with oxygen to create a breathing gas that avoids the narcotic effect of nitrogen at high pressures (Trimix).
7. Leak Detection: Due to its small atomic size and inertness, helium is used in detecting leaks in high-vacuum equipment and high-pressure containers.
8. Scientific Research: Helium’s inertness and extreme conditions (low boiling point, high speed of sound, low solubility) make it valuable for various scientific research applications.

Commercial Production of Helium

1. Natural Gas Extraction: The primary commercial source of helium is natural gas, which can contain up to 7% helium depending on the source. Plants cool the natural gas to a low temperature, at which point helium and other gases liquefy and can be separated.
2. Air Distillation: Though not as common due to its low concentration in the atmosphere, helium can technically be obtained by liquefying and distilling air. This process is not commercially viable due to the high energy cost and low yield.
3. Radioactive Decay: While not a commercial method, it’s worth noting that helium is also produced through the alpha decay of heavy radioactive elements where an alpha particle (helium nucleus) is emitted.
4. Refining and Storage: Once extracted, helium is purified to remove any remaining nitrogen, methane, hydrogen, and other impurities. It’s then either liquefied for transport

Health Effects of Helium

1. Inhalation Risks: Inhaling helium directly from a pressurized container can be dangerous, leading to dizziness, light-headedness, or even asphyxiation due to displacement of oxygen in the lungs.
2. Asphyxiation Hazard: Since helium is lighter than air, it can accumulate in the upper parts of enclosed spaces, displacing oxygen and posing a risk of asphyxiation when inhaled in large quantities.
3. Effect on Voice: Breathing in helium temporarily changes the sound of a person’s voice, making it much higher. This is due to the speed of sound being faster in helium than in air, but it should be noted that this practice is risky and can lead to serious health effects.
4. Non-Toxic Nature: Helium is non-toxic and chemically inert, meaning it doesn’t react with other elements or compounds within the human body. It poses no chronic health risks when handled properly.
5. Minimal Biological Role: Helium has no known biological role in humans or animals, and it’s not absorbed by the body. Any inhaled helium is exhaled and does not accumulate in the body.

Environmental Effects of Helium

1. Low Reactivity: Being a noble gas, helium is chemically inert and doesn’t react with the environment. It doesn’t contribute to chemical smog, acid rain, or greenhouse gas effects.
2. Non-renewable Resource: Helium is a finite, non-renewable resource primarily extracted from natural gas. Excessive consumption and wastage can deplete available reserves critical for scientific and medical instruments.
3. Impact on Wildlife: There are no direct adverse effects of helium on plants or animals due to its inertness. However, the release of balloons filled with helium can lead to litter and pose ingestion and entanglement risks to wildlife.
4. Atmospheric Escape: Once released into the atmosphere, helium eventually escapes into space due to its light nature. This loss is permanent and contributes to the depletion of earthly helium resources.
5. Minimal Greenhouse Effect: Helium doesn’t contribute to the greenhouse effect or global warming. Its environmental footprint is mostly related to the energy used and emissions from its extraction and purification processes.

What Do We Use Helium For?

Helium is primarily used in cryogenics, as a lifting gas, in gas chromatography, for leak detection, in arc welding, and in deep-sea diving mixtures.

Is Helium Running Out?

Yes, helium is a finite resource with increasing concerns about its depletion due to limited reserves and rising demand in various industries.

Why Can’t Helium Be Made?

Helium is formed through natural processes like radioactive decay and nuclear fusion in stars, not by chemical synthesis, making artificial production impractical.

Can Helium Be Used as Gas?

Yes, helium is used as a gas in many applications due to its inertness, including as a protective atmosphere, in balloons, and in scientific research.

What Does Helium Do to You?

Inhaling helium temporarily changes your voice pitch; however, it can be dangerous, causing dizziness, asphyxiation, and in severe cases, death due to oxygen displacement.

Where Does Helium Come From?

Helium is extracted from natural gas reserves where it accumulates over millions of years from radioactive decay of uranium and thorium.

What Is the Purpose of Helium?

The purpose of helium is diverse: from enabling MRI machines in medicine, lifting balloons, protecting welds, to conducting scientific research due to its unique properties.

Helium serves as an invaluable resource across various fields due to its unique properties. Understanding how to utilize helium effectively is crucial in industries ranging from healthcare to aerospace. As reserves dwindle, appreciating its uses, conserving it, and seeking alternatives become increasingly important. This guide aims to equip you with knowledge and tips to navigate the world of helium efficiently.