List of data references for chemical elements
Values for many properties of the elements, together with various references, are collected on these data pages.
References for chemical elements
Abundance of the chemical elements
- List of chemical elements — atomic mass, atomic number, symbol, name
- Abundance of the chemical elements
- Abundances of the elements (data page) — Earth's crust, sea water, Sun and solar system
- Abundance of elements in Earth's crust
- Atomic radii of the elements (data page) — atomic radius (empirical), atomic radius (calculated), van der Waals radius, covalent radius
- Boiling points of the elements (data page) — Boiling point
- Critical points of the elements (data page) — Critical point
- Densities of the elements (data page) — Density (solid, liquid, gas)
- Elastic properties of the elements (data page) — Young's modulus, Poisson ratio, bulk modulus, shear modulus
- Electrical resistivities of the elements (data page) — Electrical resistivity
- Electron affinity (data page) — Electron affinity
- Electron configurations of the elements (data page) — Electron configuration
- Electronegativities of the elements (data page) — Electronegativity (Pauling scale)
- Hardnesses of the elements (data page) — Mohs hardness, Vickers hardness, Brinell hardness
- Heat capacities of the elements (data page) — Heat capacity
- Heats of fusion of the elements (data page) — Heat of fusion
- Heats of vaporization of the elements (data page) — Heat of vaporization
- Ionization energies of the elements (data page) — Ionization energy (in eV) and molar ionization energies (in kJ/mol)
- List of oxidation states of the elements — Oxidation state
- Melting points of the elements (data page) — Melting point
- Speeds of sound of the elements (data page) — Speed of sound
- Thermal conductivities of the elements (data page) — Thermal conductivity
- Thermal expansion coefficients of the elements (data page) — Thermal expansion
- Vapor pressures of the elements (data page) — Vapor pressure
The abundance of the chemical elements is a measure of the occurrence of the chemical elements relative to all other elements in a given environment. Abundance is measured in one of three ways: by the mass-fraction (the same as weight fraction); by the mole-fraction (fraction of atoms by numerical count, or sometimes fraction of molecules in gases); or by the volume-fraction. Volume-fraction is a common abundance measure in mixed gases such as planetary atmospheres, and is similar in value to molecular mole-fraction for gas mixtures at relatively low densities and pressures, and ideal gas mixtures. Most abundance values in this article are given as mass-fractions.
For example, the abundance of oxygen in pure water can be measured in two ways: the mass fraction is about 89%, because that is the fraction of water's mass which is oxygen. However, the mole-fraction is 33.3333...% because only 1 atom of 3 in water, H2O, is oxygen. As another example, looking at the mass-fraction abundance of hydrogen and helium in both the Universe as a whole and in the atmospheres of gas-giant planets such as Jupiter, it is 74% for hydrogen and 23–25% for helium; while the (atomic) mole-fraction for hydrogen is 92%, and for helium is 8%, in these environments. Changing the given environment to Jupiter's outer atmosphere, where hydrogen is diatomic while helium is not, changes the molecular mole-fraction (fraction of total gas molecules), as well as the fraction of atmosphere by volume, of hydrogen to about 86%, and of helium to 13%.The abundance of chemical elements in the universe is dominated by the large amounts of hydrogen and helium which were produced in the Big Bang. Remaining elements, making up only about 2% of the universe, were largely produced by supernovae and certain red giant stars. Lithium, beryllium and boron are rare because although they are produced by nuclear fusion, they are then destroyed by other reactions in the stars. The elements from carbon to iron are relatively more abundant in the universe because of the ease of making them in supernova nucleosynthesis. Elements of higher atomic number than iron (element 26) become progressively rarer in the universe, because they increasingly absorb stellar energy in their production. Also, elements with even atomic numbers are generally more common than their neighbors in the periodic table, due to favorable energetics of formation.
The abundance of elements in the Sun and outer planets is similar to that in the universe. Due to solar heating, the elements of Earth and the inner rocky planets of the Solar System have undergone an additional depletion of volatile hydrogen, helium, neon, nitrogen, and carbon (which volatilizes as methane). The crust, mantle, and core of the Earth show evidence of chemical segregation plus some sequestration by density. Lighter silicates of aluminum are found in the crust, with more magnesium silicate in the mantle, while metallic iron and nickel compose the core. The abundance of elements in specialized environments, such as atmospheres, or oceans, or the human body, are primarily a product of chemical interactions with the medium in which they reside.
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