According to the Bohr model, or planetary model, the electrons encircle the nucleus of the atom in specific allowable paths called orbits. The electron is not allowed to occupy any of the spaces in between the orbits.

Bohr proposed that electrons do not radiate energy as they orbit the nucleus, but exist in states of constant energy which he called stationary states. This means that the electrons orbit at fixed distances from the nucleus. Bohr’s work was primarily based on the atomic emission spectra of hydrogen. This is also referred to as the planetary model of the atom.

According to the Bohr model, the electrons encircle the nucleus of the atom in specific allowable paths called orbits. When the electron is in one of these orbits, its energy is fixed. Bohr explained that electrons could be moved into different orbits (jump to excited state) with the addition of energy. When the energy is removed, the electrons return to their ground state, emitting a corresponding amount of energy – a quantum of light, or photon. This was the basis for what later became known as quantum theory. This is a theory based on the principle that matter and energy have the properties of both particles and waves, also known as wave-particle duality.

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Key Points

• According to the Bohr model, or planetary model, the electrons encircle the nucleus of the atom in specific allowable paths called orbits. The electron is not allowed to occupy any of the spaces in between the orbits.

Key Terms

atomic emission spectrum: is the pattern of lines corresponds to a different electron transition from a higher energy state to a lower energy state.

the planetary model of the atom: or Bohr model of the atom, where the electrons are described to encircle the nucleus of the atom in specific allowable paths called the orbit.

atom: The smallest possible amount of matter that still retains its identity as a chemical element. Atoms consist of a nucleus surrounded by electrons.

ground state: is the lowest energy state of the atom.

excited-state: of an atom is a state where its potential energy is higher than the ground state.

electron: each electron has a negative charge (-1) with weight so small it’s normally negligible as compared to proton or neutron.

photon: the smallest discrete amount of electromagnetic radiation. It is the basic unit of all light, carrying the energy E= hf.