nLab atomic number

Idea

The atomic number of a chemical element is the number of protons in any atomic nuclei of this element.

For instance carbon has atomic number 6.

The periodic table of chemical elements organizes them by their atomic number, together with other properties.

The corresponding number of neutrons on the nucleus tends to be close to the number of protons, hence to the atomic number of the element, but need not equal it and my differ considerably for heavy elements. These variants of neutron number for given atomic number specify the isotopes of the chemical element.

References

See also

• Wikipedia, Atomic number

Speculative analogy to characteristic classes of complex surfaces (different from but inspired by Skyrmion models for atomic nuclei):

• Michael Atiyah, Nicholas Manton, Complex Geometry of Nuclei and Atoms (arXiv:1609.02816)