![]() The negative sign in Equation 7.3.3 indicates that the electron-nucleus pair is more tightly bound when they are near each other than when they are far apart. The orbit with n = 1 is the lowest lying and most tightly bound. In his final years, he devoted himself to the peaceful application of atomic physics and to resolving political problems arising from the development of atomic weapons.Īs n decreases, the energy holding the electron and the nucleus together becomes increasingly negative, the radius of the orbit shrinks and more energy is needed to ionize the atom. (b) The energy of the orbit becomes increasingly less negative with increasing n.ĭuring the Nazi occupation of Denmark in World War II, Bohr escaped to the United States, where he became associated with the Atomic Energy Project. ![]() The atom has been ionized.įigure 7.3.2 The Bohr Model of the Hydrogen Atom (a) The distance of the orbit from the nucleus increases with increasing n. In this state the radius of the orbit is also infinite. In that level, the electron is unbound from the nucleus and the atom has been separated into a negatively charged (the electron) and a positively charged (the nucleus) ion. In 1924 Louis de Broglie proposed that electrons have a wave nature. In this model n = ∞ corresponds to the level where the energy holding the electron and the nucleus together is zero. An unexcited hydrogen atom will have its electron in this state. Where \( \Re \) is the Rydberg constant, h is Planck’s constant, c is the speed of light, and n is a positive integer corresponding to the number assigned to the orbit, with n = 1 corresponding to the orbit closest to the nucleus. Bohr described the hydrogen atom in terms of an electron moving in a circular orbit about a nucleus. The model has a special place in the history of physics because it introduced an early quantum theory, which brought about new developments in scientific thought and later culminated in. The Bohr model of the hydrogen atom explains the connection between the quantization of photons and the quantized emission from atoms. The Rydberg formula remained unexplained until the first successful model of the hydrogen atom was proposed in 1913.\] Historically, Bohr’s model of the hydrogen atom is the very first model of atomic structure that correctly explained the radiation spectra of atomic hydrogen. The Rydberg formula for hydrogen gives the exact positions of the spectral lines as they are observed in a laboratory however, at the beginning of the twentieth century, nobody could explain why it worked so well. Bohr proposed that electrons do not radiate energy as they orbit the nucleus, but exist in states of constant energy that he called stationary states. As you may guess, there are infinitely many such spectral bands in the spectrum of hydrogen because \(n_f\) can be any positive integer number. Following the discoveries of hydrogen emission spectra and the photoelectric effect, the Danish physicist Niels Bohr (1885-1962) proposed a new model of the atom in 1915. ![]() When \(n_f = 6\), we have the Humphreys series. When \(n_f = 5\), the series is called the Pfund series. When \(n_f = 4\), the series is called the Brackett series. But there are few drawbacks of Bohr model when explaining the atomic structure of atoms other than Hydrogen. When \(n_f = 3\), the series is called the Paschen series. Bohr model perfectly fits the hydrogen atom, which has a single electron and a small positively charged nucleus.
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