Scientists determined the number of electrons in an atom through experiments involving X-ray spectra and atomic charge. Key contributions came from Rutherford, who estimated nuclear charge, and Henry Moseley, who established the relationship between X-ray wavelengths and atomic numbers in 1913. The concept of atomic number, introduced by A. van den Broek in 1911, became fundamental in organizing the periodic table, superseding atomic weight as the primary classification method. This understanding was further enhanced by Niels Bohr's studies on electron shells and G.N. Lewis's discoveries regarding bonding electron pairs.
PREREQUISITESStudents of chemistry and physics, educators teaching atomic theory, and researchers interested in the historical development of atomic structure understanding.
During the 1890s and early 1900s, there were a number of scientists working on atomic structure: Rutherford, Bohr, Thomson, and many physicists, and numerous chemists.JaredPM said:How did scientists/chemists experimentally determine how many electrons an atom has?
Hydrogen, carbon, oxygen, etc...
I'm wandering what physical experiment would tell you how many electrons an atom has?
http://www.wou.edu/las/physci/ch412/perhist.htmin 1911, A. van den Broek in a series of two papers proposed that the atomic weight of an element was approximately equal to the charge on an atom. This charge, later termed the atomic number, could be used to number the elements within the periodic table. In 1913, Henry Moseley (see a picture) published the results of his measurements of the wavelengths of the x-ray spectral lines of a number of elements which showed that the ordering of the wavelengths of the x-ray emissions of the elements coincided with the ordering of the elements by atomic number. With the discovery of isotopes of the elements, it became apparent that atomic weight was not the significant player in the periodic law as Mendeleev, Meyers and others had proposed, but rather, the properties of the elements varied periodically with atomic number.
The question of why the periodic law exists was answered as scientists developed an understanding of the electronic structure of the elements beginning with Niels Bohr's studies of the organization of electrons into shells through G.N. Lewis' (see a picture) discoveries of bonding electron pairs. . . . .