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  2. Number density - Wikipedia

    en.wikipedia.org/wiki/Number_density

    The number density (symbol: n or ρ N) is an intensive quantity used to describe the degree of concentration of countable objects (particles, molecules, phonons, cells, galaxies, etc.) in physical space: three-dimensional volumetric number density, two-dimensional areal number density, or one-dimensional linear number density.

  3. Isotopes of hydrogen - Wikipedia

    en.wikipedia.org/wiki/Isotopes_of_hydrogen

    Deuterium, 2 H (atomic mass 2.014 101 777 844 (15) Da), the other stable hydrogen isotope, has one proton and one neutron in its nucleus, called a deuteron. 2 H comprises 26–184 ppm (by population, not mass) of hydrogen on Earth; the lower number tends to be found in hydrogen gas and higher enrichment (150 ppm) is typical of seawater.

  4. Deuterium - Wikipedia

    en.wikipedia.org/wiki/Deuterium

    Further, a nuisance problem of normal hydrogen is its large incoherent neutron cross section, which is nil for 2 H. The substitution of deuterium for normal hydrogen thus reduces scattering noise. Hydrogen is an important and major component in all materials of organic chemistry and life science, but it barely interacts with X-rays.

  5. Tritium - Wikipedia

    en.wikipedia.org/wiki/Tritium

    Tritium (from Ancient Greek τρίτος (trítos) 'third') or hydrogen-3 (symbol T or 3 H) is a rare and radioactive isotope of hydrogen with a half-life of ~12.3 years. The tritium nucleus (t, sometimes called a triton) contains one proton and two neutrons, whereas the nucleus of the common isotope hydrogen-1 (protium) contains one proton and no neutrons, and that of non-radioactive hydrogen ...

  6. Stable nuclide - Wikipedia

    en.wikipedia.org/wiki/Stable_nuclide

    Stable even–even nuclides number as many as three isobars for some mass numbers, and up to seven isotopes for some atomic numbers. Conversely, of the 251 known stable nuclides, only five have both an odd number of protons and odd number of neutrons: hydrogen-2 , lithium-6, boron-10, nitrogen-14, and tantalum-180m.

  7. Neutron number - Wikipedia

    en.wikipedia.org/wiki/Neutron_number

    The neutron number (symbol N) is the number of neutrons in a nuclide. Atomic number (proton number) plus neutron number equals mass number: Z + N = A. The difference between the neutron number and the atomic number is known as the neutron excess: D = N − Z = A − 2Z. Neutron number is not written explicitly in nuclide symbol notation, but ...

  8. Neutron - Wikipedia

    en.wikipedia.org/wiki/Neutron

    The atomic number determines the chemical properties of the atom, and the neutron number determines the isotope or nuclide. [7]: 4 The terms isotope and nuclide are often used synonymously, but they refer to chemical and nuclear properties, respectively. [7]: 4 Isotopes are nuclides with the same atomic number, but different neutron number.

  9. Isotopologue - Wikipedia

    en.wikipedia.org/wiki/Isotopologue

    Depending on the formula and the symmetry of the structure, there might be several isotopomers of one isotopologue. For example, ethanol has the molecular formula C 2 H 6 O. Mono-deuterated ethanol, C 2 H 5 DO or C 2 H 5 2 HO, is an isotopologue of it. The structural formulas CH 3 −CH 2 −O−D and CH 2 D−CH 2 −O−H are two isotopomers ...