Helium Chemical Properties (25 Facts You Should Know)

Helium is a noble gas element that has inert shell configuration with relative abundance of 24-25% in earth’s atmosphere. Let us discuss more facts about helium below.

Helium is a monoatomic gas that does not react with other atoms due to its stability. It is non-toxic, odorless and colorless. It is used for filling balloons and as lifting gas. It is used as cryogenics, superconducting magnets in spectroscopy applications and protective gas in crystals preparation of Si.

Helium has high binding energy and is found as one of elements in sun. Let us study more relevant facts like atomic weight, density, electron shell about helium.

Helium symbol

The chemical symbol of helium is He. The chemical name helium is derived from a Greek word ‘Helios’ meaning sun.

Atomic symbol of Helium atom, a noble gas element.

Helium group in periodic table

Helium is a group 18 element in the periodic table. It is also known as noble gas family.

Helium period in periodic table

Helium is a 1st period element. It is the second element that comes in a periodic table. It has only two electrons in its shell so it occupies the first period.

Helium block in periodic table

Helium is an s-block element. This is so as the last electron enters s orbital. He has two electrons and both enters 1s shell.

Helium atomic number

The atomic number of helium is 2. The 2 represents the charge (protons) number of the nucleus.

Helium atomic weight

The atomic weight of helium is 4. The atomic weight or mass number is almost twice the atomic number of the element.

Helium Electronegativity according to Pauling

Helium electronegativity according to Pauling scale is not yet calculated neither predicted.

Helium atomic Density

The atomic density of helium is 0.145 g/cm3. It is lighter than water which has density of 1 g/cm3.

Helium melting point

The melting point of helium is 0.95 K. The melting point is extremely low due to weak dispersion forces present in He.

Helium boiling point

The boiling point of Helium is 4.3 K. The boiling point of helium is even lower than hydrogen.

Helium Van der Waals radius

The Van der Waals radius of helium element is 140 pm. It is the distance between the two helium nuclei.

Helium ionic/covalent radius

The covalent radius of helium element is 28 pm. It is the distance between the nucleus of He and the outermost electron in 1s shell..

Helium isotopes

Isotopes are elements with same atomic number but different mass number due to difference in neutrons in the nucleus of the element. Let us discuss in details below.

Helium has a total of 9 isotopes out of which only two are stable. They are 3He and 4He. The remaining isotopes decay faster and are radioactive in nature.

The list of isotopes of helium are given below

  • 3He
  • 4He
  • 5He
  • 6He
  • 7He
  • 8He
  • 9He
  • 10He
  • The least stable among all is the 6He isotope with a half-life of few yoctoseconds.

Helium electronic shell

Electronic shell is a symbolic notation of how the electrons are distributed maintaining Hund’s and Aufbau principle in different orbits of an element. Let us check below.

The electronic shell of helium is 2 and is inert. It has only two electrons in its shell and it enters 1s orbital.

Helium energy of first ionization

The first ionization energy of helium is 2372.3 kJ/mol. The energy required to remove the first electron from a completely filled inert shell is extremely high.

Helium energy of second ionization

The second energy of ionization of helium is 5250 kJ/mol. This energy is higher than the first ionization energy as helium acquires 1s1 state.

Helium energy of third ionization

The third energy of ionization of helium is zero kJ/mol as there are no electrons left in the shell. He has only two electrons in its shell.

Helium oxidation states

The oxidation state shown by helium is only 0 (zero) as it is an inert gas element.

Helium electron configurations

The electron configuration of helium is 1s2. Every s orbital with n principal quantum number can hold a maximum of 2 electrons.

Helium CAS number

The CAS number of helium is 7440-59-7. This number is unique and can be used in database sites to find its structure and properties.

Helium ChemSpider ID

The ChemSpider ID of helium is 22423. Using this number, we can find relevant facts and properties about helium without facing tedious search.

Helium allotropic forms

Allotropes are structures of molecules or atoms to exist in different form with same physical state. Let us check below the allotropes of helium.

Helium has two allotropic forms. One is helium dimer and another one is helium trimer. Helium dimer exists due to van der waals forces of attraction.

Helium chemical classification

Based on helium chemical reactivity and properties, it can be chemically classified as

  • Helium is an inert gas element.
  • Helium belongs to noble gas family due to inert shell.
  • Helium is a non-reactive non-metal.

Helium state at room temperature

Helium is in gaseous state at room temperature as He does not react with any nearby atoms due to its inert nature.

Is helium paramagnetic?

Paramagnetism is a tendency shown by paramagnetic materials in presence of external magnetic field. Let us see if He is paramagnetic or not.

Helium is a not a paramagnetic element. It is a diamagnetic element. The reason being the only two electrons lying in 1s orbitals are paired.


Helium is a non reactive monoatomic inert gas that do not form bonds with any other atoms due to its inert stability and is used as a lifting gas and cryogenic liquid.

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