Argument
Semi-empirical mass formula
Overview
In nuclear physics, the semi-empirical mass formula (SEMF; sometimes also called the Weizsäcker formula, Bethe–Weizsäcker formula, or Bethe–Weizsäcker mass formula to distinguish it from the Bethe–Weizsäcker process) is used to approximate the mass of an atomic nucleus from its number of protons and neutrons. As the name suggests, it is based partly on theory and partly on empirical measurements. The formula represents the liquid-drop model proposed by George Gamow, which can account for most of the terms in the formula and gives rough estimates for the values of the coefficients. It was first formulated in 1935 by German physicist Carl Friedrich von Weizsäcker, and although refinements have been made to the coefficients over the years, the structure of the formula remains the same today.
The formula gives a good approximation for atomic masses and thereby other effects. However, it fails to explain the existence of lines of greater binding energy at certain numbers of protons and neutrons. These numbers, known as magic numbers, are the foundation of the nuclear shell model.
Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).
Possible passages
Found by search and not yet checked by a person; they may only mention the idea in passing.
The result is that a table of the equivalent numbers, or, as they are called, atomic weights, of all the elementary substances, comprises in itself, and scientifically explains, all the proportions in which any substance, elementary or compound, is found capable of entering into chemical combination with any other substance whatever.
John Stuart Mill, A System of Logic, Ratiocinative and Inductive
States what Semi-empirical mass formula is.
Note 16. The electric-rest force. (Page 37.) The four-vector φ = wF which is called by Minkowski the electric-rest-force (elektrische Ruh-Kraft) is very closely connected to Lorentz’s Ponderomotive force, or the force acting on a moving charge. If ρ is the density of charge, we have, when ε = 1, μ = 1, _i.e._, for free space ρ₀φ₁ = ρ₀[w₁ F₁₁ w₂ F₁₂ + w₃ F₁₃ + w₄ F₁₄] = ρ₀/(√(1 - V²/_c²_)) [_d__{_x_} + 1/_c_ (_v₂_…
Albert Einstein, The Principle of Relativity
States what Semi-empirical mass formula is.
It was supposed, until radio-activity was discovered, that atoms were indestructible and unchangeable. Substances which were not compounds were called “elements”. The Russian chemist Mendeleev discovered that the elements can be arranged in a series by means of progressive changes in their properties; in his time, there were gaps in this series, but most of them have since been filled by the discovery of new…
Bertrand Russell, Philosophy
States what Semi-empirical mass formula is.
Related ideas
- Carl Friedrich von Weizsäcker
- Wave function
- Mass
- Scientific theory
- Atomic nucleus
- Niels Bohr
- Periodic table
- Empirical evidence
- Wiley (publisher)
- Nuclear shell model
Place in the tradition
Part of Scientific realism.
Explore Semi-empirical mass formula in the interactive graph →