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Transitions are also possible between excited states, eg. The first excited state is n = 2 the second excited state is n = 3. It can absorb energy, and move to an excited state n > 1. All allowed electron energy states therefore have negative energies.Ģ) The hydrogen atom is normally in the ground state, and the electron has principle quantum number (or energy level) n = 1. As the electron approaches the proton, it loses energy. This integer, n, becomes known as the principal quantum number, or energy level of the electron.īohr’s model established three general points.ġ) Zero energy was designated as the point at which electron and proton are completely separated, i.e. He deduced: En = !RH / n2 where RH = Rydberg constant = 2.180 × 10!18J, and n = integer = 1, 2, 3. He had no theoretical basis for this assumption, merely the need to explain the observed experimental result. Bohr boldly assumed that only certain definite energies of the electron were allowed.
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Such a model predicts a continuous range of possible electron energies, which would give rise to a continuous rather than a line spectrum. Energy would then be absorbed/radiated as the electron changed the radius of its orbit.The electrostatic attractive force between the positively charged proton and the negatively charged electron is balanced by the centrifugal force due to the circular motion.Bohr assumed a central proton, about which an electron moves in a circular orbit.This model of the Hydrogen atom is a theoretical explanation of atomic spectra based on classical mechanics.1) the continuous spectrum obtained from white light 2) the line spectrum obtained from atoms So we have seemingly contradictory results.
#NS2 NP3 VALENCE SHELL SERIES#
The first of these series to be discovered was the Balmer Series, which lies partly in the visible region. These gaseous hydrogen atoms emit radiation (light) at wavelengths which may be grouped into series. Hydrogen atoms are produced when an electric discharge is struck through gaseous hydrogen.So we say that the energy of an atom is exists in certain fixed quantities.As photons are produced when an electron moves from one energy level to another it follows that the energy levels for an electron in an atom are limited to specific values.As photons have only certain wavelengths, it follows that they can only have certain energies.Atomic spectra are characteristic to the element in question can be used for identification.This is not a continuous spectra the emitted light creates a line spectra in which each line corresponds to a specific wavelength of light.If an element is vaporized and then excited (given more energy) photons of light are emitted as the excited electrons return to their pre - excited energy level.this is called an atomic spectra.This spectrum is continuous and contains essentially all wavelengths between 400 and 700 nm.White (or visible) light (from the sun) can be broken down into its colour components this is called a spectrum.Note that the energy of the photon is inversely proportional to wavelength, and directly proportional to frequency.The quantity h is called Planck’s constant, with a value of h = 6.626 × 10G34 J s.Work by Max Planck and Albert Einstein during the years 1900-1910 showed that light is generated as a stream of particles, called photons, whose energy is given by the Einstein equation:.Ultra violet (UV) and Infra red (IR) are two of several other regions.The eye sees only a small fraction of the electromagnetic spectrum, the Visible region, which has wavelengths ranging from 400-700 nm.The speed of light, c, the speed at which a light wave moves through space is a constant, 2.998 × 108 m sG1.A frequency of one Hertz, Hz, is one cycle per second.The number of cycles that pass a given point in unit time is the frequency, ν, of the wave.Light travels through space as a wave the wavelength, λ, is the distance between successive crests or troughs.Light, Photon Energies and Atomic Spectra Recall that we have already used these positions can also be used to predict sizes of atoms and their tendencies to gain or lose electrons.The electron configuration (the actual arrangement of the electrons) of an element can be determined from its position on the Periodic Table.As we look at the arrangements of electrons in atoms, we are paying special attention to: 1) the relative energies of the electronsĢ) the spatial locations of the electrons.