Helium Facts – Atomic Number 2 or He 1

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Helium Facts
Element cell for Helium
Periodic Table cell for the element Helium.

Helium is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Helium is the second lightest and second most abundant element in the universe. Helium mainly occurs in stars and nebulae. On Earth, we extract it from natural gas for use in balloons, cryogenics, breathing mixtures, and fusion research.

Basic Helium Facts

Name: Helium

Atomic Number: 2

Element Symbol: He

Group: 18 (although there are arguments for placing it in Group 2)

Period: 1

Block: s

Element Family: Noble Gas

Atomic Mass: 4.002602(2)

Electron Configuration: 1s2

Appearance: Helium is a colorless, odorless, and tasteless gas.

History

Discovery: First identified: Pierre Janssen in 1868. First Isolated: Sir William Ramsay in 1895.

Janssen was a French astronomer who observed a new yellow spectral line while observing a total solar eclipse in 1868. He assumed it was part of the sodium spectrum. English astronomer Norman Lockyer later observed the same line but could not link it to sodium. Together with English chemist Edward Frankland, they decided it was associated with a new element. In 1985, Scottish chemist William Ramsay isolated a gas from a sample of a mineral cleveite which contained the yellow spectral line. Swedish chemists Per Teodor Cleve and Abraham Langlet independently made the same discovery the same year in Sweden.

Name Origin: Helios, Greek god of the Sun. Lockyer and Frankland named their unknown element after the location it was first discovered, the Sun.

Helium Isotopes

The natural isotopes of helium are helium-3, which has two protons and one neutron, and helium-4, which has two protons and two neutrons. Both isotopes are stable. He-3 accounts for 1.37 x 10-4% of helium found in the atmosphere. Helium-4 is the most common form of helium. It accounts for 99.999863% of all helium in the atmosphere. There are also seven synthetic radioisotopes of the element.

Helium Uses

Helium has a wide range of applications, including:

  • Cryogenics: Used as a coolant for superconducting magnets, such as those in MRI machines.
  • Balloons and Airships: Due to its lighter-than-air properties.
  • Welding: Acts as a protective gas in arc welding.
  • Breathing Mixtures: For use in deep-sea diving and medical treatments.
  • Scientific Research: Important in experiments involving low temperatures and as a carrier gas in gas chromatography.
  • Nuclear Fusion: Helium-3 has potential use in fusion reactors.

Sources

Helium is the second most abundant element in the universe, constituting about 24% of its elemental mass. However, it is relatively rare on Earth. It occurs in:

  • Natural Gas Fields: Helium is extracted from natural gas, where it exists in concentrations up to 7%. Purification is via fractional distillation of liquefied natural gas.
  • Atmosphere: The Earth’s atmosphere contains helium at about 5.2 parts per million by volume.
  • Cosmic Sources: Helium is produced in large quantities by nuclear fusion in stars and during the Big Bang.

Health Effects

Helium has no known biological role and is considered biologically inert. While it is non-toxic, inhaling it in place of oxygen leads to asphyxiation. Prolonged exposure to high concentrations causes dizziness, nausea, and loss of consciousness.

Helium
Helium in a gas-discharge tube. (pslawinski, metal-halide.net)

Physical Data

Density: 0.000164 g/cm3

Melting Point: 0.95K (-272.20 ºC or -457.96 ºF) at 2.5 MPa

Boiling Point: 4.222 K (-2683928 ºC or -452.070 ºF)

Triple Point: 2.177 K at 5.043 kPa

Critical Point: 5.1953 K at 227.45 kPa

State at 20ºC: Gas

Heat of Fusion: 0.0138 kJ/mol

Heat of Vaporization: 0.0829 kJ/mol

Molar Heat Capacity: 20.78 J/mol·K

Magnetic Ordering: Diamagnetic

Crystal Structure: Hexagonal close-packed (hcp)

Helium Atom
Electron shell configuration of a helium atom.

Atomic Data

Atomic Radius: 1.40 Å

Covalent Radius: 0.37 Å

Van der Waals Radius:  1.40 Å

Electron Affinity: not stable

Electronegativity: unknown

1st Ionization Energy: 2372.3 kJ/mol

2nd Ionization Energy: 5250.5 kJ/mol

Common Oxidation State: 0

Interesting Helium Facts

  • Helium is the lightest and least dense of the noble gases.
  • Helium does not readily form compounds, but a few exist, such as helium fluorohydride (HHeF).
  • Helium was the first element to be discovered outside of Earth. The first evidence of the existence of helium was from spectroscopy data from the Sun.
  • Even though helium is relatively rare on Earth, it is the second most abundant element. Helium accounts for roughly 24% of all elemental mass of the universe.
  • Helium has the lowest melting and boiling points of all the elements. Creating solid and liquid helium takes extreme pressures and low temperatures. It is the only element that cannot be solidified using only temperature.
  • Helium gas is colorless, tasteless, odorless, non-toxic and inert.
  • Most helium gas is extracted from natural gas deposits.
  • Radioactive emissions from α decay are helium nuclei.
  • Helium is the second least reactive noble gas after neon.
  • Inhaling helium gas makes a person’s voice sound higher (it changes the timbre but does not actually raise the pitch of a person’s voice).
  • Even though helium was discovered by its yellow spectral line, ionized helium gas has a reddish orange glow.

Learn more about elements on the periodic table.

References