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Gadolinium is a chemical element; it has symbol Gd and atomic number 64. Gadolinium is a silvery-white metal when oxidation is removed. It is a malleable and ductile rare-earth element. Gadolinium reacts with atmospheric oxygen or moisture slowly to form a black coating. Gadolinium below its Curie point of 20 °C (68 °F) is ferromagnetic, with ...
The Bohr model is a relatively primitive model of the hydrogen atom, compared to the valence shell model. As a theory, it can be derived as a first-order approximation of the hydrogen atom using the broader and much more accurate quantum mechanics and thus may be considered to be an obsolete scientific theory.
In 1913, Niels Bohr proposed a model of the atom, giving the arrangement of electrons in their sequential orbits. At that time, Bohr allowed the capacity of the inner orbit of the atom to increase to eight electrons as the atoms got larger, and "in the scheme given below the number of electrons in this [outer] ring is arbitrary put equal to the normal valency of the corresponding element".
Electron configuration was first conceived under the Bohr model of the atom, and it is still common to speak of shells and subshells despite the advances in understanding of the quantum-mechanical nature of electrons. An electron shell is the set of allowed states that share the same principal quantum number, n, that electrons may occupy.
Atomic orbitals are basic building blocks of the atomic orbital model (or electron cloud or wave mechanics model), a modern framework for visualizing submicroscopic behavior of electrons in matter. In this model, the electron cloud of an atom may be seen as being built up (in approximation) in an electron configuration that is a product of ...
The Bohr model was based on the assumed quantization of angular momentum according to = =. According to de Broglie, the electron is described by a wave, and a whole number of wavelengths must fit along the circumference of the electron's orbit: n λ = 2 π r . {\displaystyle n\lambda =2\pi r.}
The Bohr–Sommerfeld model (also known as the Sommerfeld model or Bohr–Sommerfeld theory) was an extension of the Bohr model to allow elliptical orbits of electrons around an atomic nucleus. Bohr–Sommerfeld theory is named after Danish physicist Niels Bohr and German physicist Arnold Sommerfeld. Sommerfeld showed that, if electronic orbits ...
Isotopes of gadolinium (64Gd) Naturally occurring gadolinium (64 Gd) is composed of 6 stable isotopes, 154 Gd, 155 Gd, 156 Gd, 157 Gd, 158 Gd and 160 Gd, and 1 radioisotope, 152 Gd, with 158 Gd being the most abundant (24.84% natural abundance). The predicted double beta decay of 160 Gd has never been observed; only a lower limit on its half ...