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A helium atom is an atom of the chemical element helium. ... The total ground state energy of the helium atom is −79.005 154 539 (25) eV, [8] or −2.903 385 83 (13
The helium atom. Depicted are the ... For these reasons and the small size of helium monatomic molecules, ... Of the 2014 world helium total production of about 32 ...
Diagram of a helium atom, showing the electron probability density as shades of gray. The atomic radius of a chemical element is a measure of the size of its atom, usually the mean or typical distance from the center of the nucleus to the outermost isolated electron. Since the boundary is not a well-defined physical entity, there are various ...
Just as atomic units are given in terms of the atomic mass unit (approximately the proton mass), the physically appropriate unit of length here is the Bohr radius, which is the radius of a hydrogen atom. The Bohr radius is consequently known as the "atomic unit of length". It is often denoted by a 0 and is approximately 53 pm. Hence, the values ...
Helium also has a very low boiling point (-268.9°C or -452°F), allowing it to remain a gas even in super-cold environments, an important feature because many rocket fuels are stored in that ...
On the periodic table of the elements, atom size tends to increase when moving down columns, but decrease when moving across rows (left to right). [71] Consequently, the smallest atom is helium with a radius of 32 pm, while one of the largest is caesium at 225 pm. [72]
The helium atom is small with the radius of the outer electron shell at 0.29 Å. [2] Helium is a very hard atom with a Pearson hardness of 12.3 eV. [3] It has the lowest polarizability of any kind of atom, however, very weak van der Waals forces exist between helium and other atoms.
Each distinct atomic number therefore corresponds to a class of atom: these classes are called the chemical elements. [5] The chemical elements are what the periodic table classifies and organizes. Hydrogen is the element with atomic number 1; helium, atomic number 2; lithium, atomic number 3; and so on.