Bohr ModelElectrons orbit the nucleus in fixed paths or "shells"Energy is absorbed or released when electrons jump between orbitsQuantum Mechanical ModelElectrons do not follow fixed paths but exist in probability zones called orbitalsBased on complex mathematics and quantum physicsSimilarities:Both describe a central nucleus with electrons surrounding itBoth attempt to explain atomic behavior and structureDifferences:Bohr's model uses fixed orbits; quantum model uses electron cloudsQuantum model is more accurate and widely accepted today