Who discovered the atomic number and how?

The atomic number, which is the number of protons in the nucleus of an atom, was discovered by Moseley through the use of X-ray spectroscopy. In his experiments, Moseley applied an electron gun to fire electrons at various elements, which resulted in the emission of X-rays when the electrons interacted with the atoms. By measuring the wavelength of the emitted X-rays, he was able to establish a systematic relationship between the frequency of the X-rays produced and the atomic number of the elements.

This discovery was significant because it led to the reorganization of the periodic table based on atomic number rather than atomic mass, clarifying the arrangement of elements and demonstrating that the atomic number is a fundamental property of elements. Moseley’s work provided a deeper understanding of atomic structure and solidified the concept of the atomic number as a key characteristic distinguishing one element from another.