Isotone Isotone Two nuclides are isotones if they have the same neutron number "N", but different proton number "Z". For example, boron-12 and carbon-13 nuclei both contain 7 neutrons, and so are isotones. Similarly, S, Cl, Ar, K, and Ca nuclei are all isotones of 20 because they all contain 20 neutrons. Despite its similarity to the Greek for "same stretching", the term was formed by the German physicist K. Guggenheimer by changing the "p" in "isotope" from "p" for "proton" to "n" for "neutron". The largest numbers of observationally stable nuclides exist for isotones 50 (five: Kr, Sr, Y, Zr,
Atomic orbital polynomial series, and exponential and trigonometric functions. (see hydrogen atom). For atoms with two or more electrons, the governing equations can only be solved with the use of methods of iterative approximation. Orbitals of multi-electron atoms are "qualitatively" similar to those of hydrogen, and in the simplest models, they are taken to have the same form. For more rigorous and precise analysis, numerical approximations must be used. A given (hydrogen-like) atomic orbital is identified by unique values of three quantum numbers: , , and . The rules restricting the values of the quantum numbers, and their energies (see below), explain