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Proposed the Bohr Model in 1915. Because the Bohr Model is a modification of the earlier Rutherford Model, some people call Bohr's Model the Rutherford-Bohr Model. The modern model of the atom is based on quantum mechanics. The Bohr Model contains some errors, but it is important because it describes most of the accepted features of atomic theory without all of the high-level math of the modern version. Unlike earlier models, the Bohr Model explains the Rydberg formula for the spectral emission lines of atomic hydrogen. The Model is a planetary model in which the negatively-charged electrons orbit a small, positively-charged nucleus similar to the planets orbiting the Sun (except that the orbits are not planar).

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In this model, the atom is composed of electrons surrounded by a "soup" of positive charge to balance the electrons' negative charges, like negatively charged “plums” surrounded by positively charged “pudding”. The 1904 Thomson model was disproved by Hans Geiger's and Ernest Marsden's 1909 gold foil experiment.

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Experiments with gases that first became possible at the turn of the nineteenth century led Dalton in 1803 to identify a modern theory of the atom that proposed that all matter was composed of atoms, indivisible and indestructible building blocks. While all atoms of an element were identical, different elements had atoms of differing size and mass.

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In 1926, he formulated a wave equation that accurately calculated the energy levels of the electrons in the atom.

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In Manchester around 1911, he was the first to discover that atoms have a small charged nucleus that is surrounded by a largely empty space and are circled by electrons. It later became known as the Rutherford (Planetary) Model of the atom.

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In the 5th century B.C.(Greece), Leucippus and Democritus started creating a model that stated that matter consists of invisible particles called atoms and a void (empty space). He stated that atoms are indestructible and unchangeable.