Editing Spin quantum number (section)

{{Short description|Quantum number parameterizing spin and angular momentum}}
{{Use American English|date=January 2019}}

{{Technical|date=February 2024|talk=Too technical}}

In [[physics]] and chemistry, the '''spin quantum number''' is a [[quantum number]] (designated '''{{mvar|s}}''') that describes the intrinsic [[angular momentum]] (or spin angular momentum, or simply [[Spin (physics)|''spin'']]) of an [[electron]] or other [[Elementary particle|particle]]. It has the same [[Value (mathematics)|value]] for all particles of the same type, such as {{mvar|s}} = {{sfrac|1|2}} for all electrons. It is an integer for all [[boson]]s, such as [[Photon|photons]], and a [[Half-integer|half-odd-integer]] for all [[fermions]], such as electrons and [[Proton|protons]].

The component of the spin along a specified [[Coordinate system|axis]] is given by the '''spin magnetic quantum number''', conventionally written '''{{mvar|m}}<sub>{{mvar|s}}</sub>'''.<ref name="Pauling 1960">{{cite book | last=Pauling | first=Linus | title=The nature of the chemical bond and the structure of molecules and crystals: an introduction to modern structural chemistry | publication-place=Ithaca, N.Y. | publisher=Cornell University Press | date=1960 | isbn=0-8014-0333-2 | oclc=545520 | page=}}</ref><ref>{{cite web|title=ISO 80000-10:2019|url=https://www.iso.org/standard/64980.html|publisher=[[International Organization for Standardization]]|access-date=2019-09-15}}</ref> The value of {{mvar|m}}<sub>{{mvar|s}}</sub> is the component of spin angular momentum, in units of the [[reduced Planck constant]] {{mvar|ħ}}, parallel to a given direction (conventionally labelled the {{mvar|z}}–axis). It can take values ranging from +{{mvar|s}} to −{{mvar|s}} in integer increments. For an electron, {{mvar|m}}<sub>{{mvar|s}}</sub> can be either {{sfrac|+|1|2}} or {{sfrac|−|1|2}} .