WebElements Periodic Table of the Elements | Helium

Properties of helium atoms

The electron affinity of helium is 0 kJ mol^-1.

Ionisation Energies

This section includes ionisation energies of helium.

Ionisation energy number	Enthalpy /kJ mol^-1
1st	2372.3
2nd	5250.5

Ionisation energies of He

Electronic configuration

The following represents the electronic configuration and its associated term symbol for the ground state neutral gaseous atom. The configuration associated with helium in its compounds is not necessarily the same.

Ground state electron configuration: 1s²
Shell structure: 2
Term symbol: ¹S₀

Kossel shell structure of He
A schematic representation of the shell structure of helium - not what the atom of helium "looks like".

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H	He
F	Ne

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Helium
- Essential data: names, symbol, atomic number, and atomic weight; block, period, and group in periodic table; description; standard state; registry number; and isolation
- History: meaning of name; discovery; and history of the element
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Helium around us
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- Geology: Abundance of elements in the universe; the sun; meteorites; Earth's crust; oceans; and streams
- Biology: Abundance in humans; biological role; and health hazards)
Helium compounds
- Compounds: halides, oxides, sulfides, hydrides, and complexes; lattice energies; and reduction potentials
- Electronegativities: Pauling; Sanderson; Allred Rochow; Mulliken-Jaffe; and Allen
- Bond enthalpies of diatomic species
- Lattice energies
Element properties
- Physics properties: Boiling point; melting point; density; molar volume; thermal conductivity; and electrical resistivity; bulk modulus; critical temperature; superconductivity temperature; hardness (mineralogical, Brinell, and Vickers); linear expansion coefficient; Poisson's ratio; reflectivity; refractive index; rigidity modulus; Young's modulus; velocity of sound
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- Reactions of calcium: reactions of helium with air; water; halogens; acids; and bases
- Crystal structure
- Thermochemistry: enthalpies of atomization, fusion, and vaporization; thermodynamic properties
Atom properties
- Electron shell properties: Electronic configuration; term symbol; electron affinity; ionization energies; and atomic spectra
- Atom sizes: atomic radius; Shannon and Pauling ionic radii; covalent radius; metallic radius; element bond length; and Van der Waals radius
- Atomic orbital properties: effective nuclear charge; electron binding energies; and valence orbital radii maxima
Nuclear properties
- Isotopes: isotope abundances; radioactive isotopes; isotope masses; nuclear spins; and nuclear magnetic moment
- NMR properties: frequencies; isotopes; magnetogyric ratios; quadrupole moments; receptivities; and relative sensitivities

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