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Moseley's law
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X-ray frequency relates to atomic number.
√f ∝ (Z − b) for characteristic X-ray lines; it showed that atomic number, not mass, orders the elements, and predicted missing elements.
Corrected the periodic table.
b ≈ 1 for K_α lines.
In more detail
Moseley's law relates the frequency of characteristic X-rays to the atomic number Z, showing that the square root of the frequency is roughly proportional to Z minus one.
Real-world uses
- Moseley's law helped order the periodic table by atomic number.
- It is used to identify elements in X-ray spectroscopy.
- Physicists used Moseley's law to order the elements by atomic number, which corrected some errors in the periodic table.
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Frequently asked questions
Why was it important?
It showed that atomic number, not atomic mass, determines element identity.
Who discovered it?
Henry Moseley, in 1913.
Why is atomic number more fundamental than mass?
Atomic number counts the protons, which decides the chemistry, while mass can vary between isotopes.
Related topics in Atomic & Nuclear Physics
Franck–Hertz experiment · Characteristic X-rays · Continuous X-ray spectrum · X-ray diffraction · Electron configuration · Atomic mass unit