The proposal in the development of the modern model of the atom that preceded others was made by Niels Bohr. In 1913, Bohr proposed his model of the atom, which incorporated the concept of quantized energy levels for electrons.
Prior to Bohr's model, scientists like J.J. Thomson and Ernest Rutherford had made significant contributions to atomic theory, but they couldn't explain certain phenomena observed in the spectral lines of elements.
Bohr's key proposal was that electrons orbit the nucleus in discrete, quantized orbits, and electrons could only transition between these orbits by absorbing or emitting specific amounts of energy.
This explained the spectral lines observed in the hydrogen spectrum and provided a more accurate depiction of atomic structure. Bohr's model was a crucial step in the development of the modern atomic model and laid the groundwork for further advancements in quantum mechanics.