![]() ![]() Pfund Series: Pfund series is formed when an electron jumps from any one of the higher orbit to fifth orbit. It is observed in middle IR region.īrackette Series: Brackette series is formed when an electron jumps from any one of the higher orbit to fourth orbit. Paschen Series: Paschen series is formed when an electron jumps from any one of the higher orbit to third orbit. Balmer Series: Balmer series is formed when an electron jumps from any one of the higher orbit to second or bit. Lyman Series: Lyman series is formed when an electron jumps from any one of the higher orbit to first orbit. Hydrogen spectrum contains 5 series of lines. Bohr’s theory explained the atomic spectrum of hydrogen and established new and broadly applicable principles in quantum mechanics. The electron of hydrogen atom gets excited to various excited levels and deexcited to form various spectral lines in various regions is called hydrogen spectrum. Only certain electron orbits are permitted. Electromagnetic energy will be absorbed or emitted if an electron moves from one orbit to another. The Bohr model of the atom, a radical departure from earlier, classical descriptions, was the first that incorporated quantum theory and was the predecessor of wholly quantum-mechanical models. Hydrogen Spectrum : When hydrogen gas is subjected to silent electric discharge. The simplest example of the Bohr Model is for the hydrogen atom (Z 1) or for a hydrogen-like ion (Z > 1), in which a negatively charged electron orbits a small positively charged nucleus. Bohr model, description of the structure of atoms, especially that of hydrogen, proposed (1913) by the Danish physicist Niels Bohr. The emitted or absorbed energy is given by ΔE = E 2 − E 1 = hϑĥ) The angular momentum of an electron moving around the nucleus is quantized. and are also designated by K, L, M, ….ģ) As long as an electron revolves in a permitted orbit it neither loose nor gain energy hence these orbits are called stationary orbits.Ĥ) When an elctron jumps from a lower orbit to a higher orbit, it absorbs energy when an electron jumps from higher orbit to lower orbit, it emits energy. Bohr's model and postulates do not explain this phenomenon.1) The electron in an atom revolve round the nucleus in certain fixed circular paths called orbits (or) shells.Ģ) Each orbit is associated with fixed energy is called energy level. Spectral lines undergo splitting when a sample of gas is affected by an electric field (Stark effect) and magnetic field (Zeeman effect).These are referred to as hyperfine spectral lines. Bohr's model does not explain the presence of hyperfine lines. Each spectral line, when examined at higher magnification, actually consists of a number of smaller fine lines. ![]() The accuracy decreases as the effective nuclear charge of an atom or ion increases (due to greater number of protons). Predictions made by Bohr’s model is only accurate for the hydrogen atom.Bohr's model cannot predict the relative intensity (brightness) of the spectral lines.In other words, his model does not explain why electrons can remain in their orbits without spiralling into the nucleus due to electrostatic attraction. Bohr does not provide an explanation to 'stationary states' of electrons. Bohr diagrams show electrons orbiting the nucleus of an atom somewhat like planets orbit around the sun.Circular motion of electrons is from classical physics while the quantisation of its momentum and energy of orbits is from quantum physics. Bohr's model combines principles from both classical and quantum physics.$$\Delta E_ J$$ Limitations of Bohr's Atomic Modelīohr's model of the atom has several limitations. An electron can transition between orbits by absorbing or releasing energy that is exactly equal to the difference in energy of orbits, consistent with the law of conservation of energy.Įlectron excitation occurs when an electron absorbs energy to move to an orbit of higher energy.Įlectron relaxation occurs when an electron moves to a lower orbit, releasing energy in the form of electromagnetic radiation (photon). In these orbits, electrons exist in 'stationary states' and do not emit energy.īohr’s model of the atom describes electrons orbiting in stable energy levels as opposed to Rutherford's model in which electrons' motion was not described.Ģ. Electrons revolve around the nucleus in circular orbits with discrete radii and quantised energies. Niels Bohr proposed three postulates in his atomic model:ġ. – Rydberg's equation Bohr's Model of the Atom ![]()
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