The Rutherford atomic model is an atomic model developed by British physicist Ernest Rutherford. Ernest Rutherford postulated that the positive charge in an atom is concentrated in a small region called the nucleus at the center of the atom, with electrons orbiting around it. material properties
Rutherford-Modell des Atoms
ÖRutherford-Modell des AtomsIt is an atomic model by British physicist Ernest Rutherford. Rutherford's new atomic model is based on experimental results obtained fromGeiger-Marsden experiments(also calledRutherford's gold leaf experiment). The Geiger-Marsden experiments were conducted between 1908 and 1913 by Hans Geiger (of fame as a Geiger counter) and Ernest Marsden (a 20-year-old student who had not yet received his bachelor's degree) under the supervision of Ernest Rutherford.
Rutherford's idea was to aim high-energy alpha particles at a thin metal plate and measure how a beam of alpha particles scatters when it hits a thin metal plate. A narrow collimated beam of alpha particles was directed at a gold foil about 1 µm thick (about 10,000 atoms thick).alpha particlethey are energeticHelium nuclei (typically around 6 MeV). Alpha particles, which are about 7,300 times heavier than electrons, have a positive charge of +2e. Due to their relatively much larger mass, alpha particles are not significantly deflected from their orbit by theelectronsin Metallatomen.
In accordance withThomson modelIf an alpha particle collided with an atom in plum pudding, it would simply fly away in a straight line, deflecting its trajectory by no more than a fraction of a degree. But in Geiger and Marsden's experiment, they saw that most of the particles scatter at very small angles, but, and this was the big surprise, a very small fraction of them scatter at very large angles, approaching 180° (i.e. they pulled back). ).
In Rutherford's words:
"It's almost as incredible as shooting a 15-inch projectile at a piece of tissue paper.and he came back and hit you.
Rutherford assumed that there must be a very large force to deflect the alpha particle backwards. Such a force could only be provided as a result of a collision with a massive target or interaction with a strong electric or magnetic field. In earlier experiments it was shown that the displacements had to be of electrical or possibly magnetic origin.
As a result, Rutherford abandoned Thomson's model. The Geiger-Marsden experiments were a seminal series of experiments in which scientists each discovered thisAtomcontains a nucleus (whose diameter is of the order of 10-14m.), where all of its positive charge and most of its mass is concentrated in a small region called the nucleus. In Rutherford's atom, the diameter of its sphere (about 10-10m) influence is determined by its electrons. In other words, the core only occupies about 10-12of the total volume of the atom or less (the nuclear atom is mostly empty space) but contains all of the positive charge and at least 99.95% of the total mass of the atom.
Based on these results, Ernest Rutherford proposed a new model of the atom. He postulated that the positive charge in an atom is concentrated in a small region (compared to the rest of the atom) called the nucleus, at the center of the atom, where electrons orbit around it. Also, the nucleus accounts for most of the mass of the atom.
Is an atom empty space?
the volume of an atomIt's about15 orders of magnitudegreaterthan the volume of a nucleus. ForUranus-Atom, ÖRaio de van der WaalsIt's about186 hours = 1.86 × 10−10Metro. O Raio de Van der Waals, rC, of an atom is the radius of an imaginary rigid sphere representing the closest approach distance to another atom. Assuming a spherical shape, theCareerAtom has a volume of approx.26,9×10−30Metro3. But this "huge" space is mainly occupied by electrons, because theCenterbusy just around1721×10−45Metro3from the universe. Together, these electrons weigh only a fraction (e.g. 0.05%) of the entire atom.
It may appear that space is actually matterfile,but it is not. because ofQuantum Nature of Electrons, Electrons are not point particles, they are scattered throughout the atom. Classical description cannot be used to describe things at the atomic level. At the atomic level, physicists have discovered that quantum mechanics describes things very well at this level. The locations of particles in quantum mechanics are not at an exact position, they are described by aprobability density function. Therefore, the space in an atom (between the electrons and an atomic nucleus) is not empty, but is instead filled with an electron probability density function (commonly known as "electron cloud“).
Failure of the Rutherford model
It should be noted that Rutherford's atomic model was not the first model to propose a nuclear structure. The idea of a nuclear structure was proposed by a Japanese physicist in early 1903.Hantaro Nagaoka, who rejected Thomson's model on the grounds that opposing allegations were impenetrable.Saturn-Modell des Atomsand according to this model the atom consists of a massive positive center surrounded by several orbiting electrons, in the manner of Saturn and its rings.
The Nagaoka planetary model had two predictions:
- a very massive atomic center (in analogy to a very massive planet)
- Electrons orbiting the nucleus and held together by electrostatic forces
Both predictions were successfully confirmed by Ernest Rutherford in 1911, but other details of the model were wrong. Although Rutherford's atomic model is very close to the modern atomic concept, it was based on classical physics. But neither classical physics nor Rutherford's model can explain the following problem. Why are negatively charged electrons prevented from falling into the positively charged nucleus? The forces between electrically charged static particles are determined byCoulomb Leus:
Rutherford suggested that the electrons might have been spinning in orbits around the nucleus.in classical mechanicsA condition for the dynamic stability of such systems of rotating particles is that only attractive forces act between their components.
Classical physics also states that any accelerated electric charge (whether oscillating or rotating)emits electromagnetic radiation. As a result, an electron orbiting within an atom must continuously lose energy and spiral towards the nucleus in fractions of a second. In fact, physicists have calculated that the electron should lose all of its energy and spiral into the proton in about 0.000000000001 seconds, meaning each atom shouldn't exist longer than 10-12seconds.
The young Danish physicist solved the problem of the stability of electrons in an atomNils BohrCollaborated with Ernest Rutherford at the University of Manchester in 1913. His adopted modelPlancks Quantenhypotheseand he proposed a model in which the electrons in an atom should revolve around the nucleus, but could only do so in a finite set of orbits. He postulated that an atom emits or absorbs energy only in discrete quanta corresponding to the absorption or radiation of an atom.Photon.
References:
Nuclear and Reactor Physics:
- J. R. Lamarsh, An Introduction to Nuclear Reactor Theory, 2. Aufl., Addison-Wesley, Reading, MA (1983).
- J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3. Aufl., Prentice-Hall, 2001, ISBN: 0-201-82498-1.
- WM Stacey, Nuclear Reactor Physics, John Wiley & Sons, 2001, ISBN: 0-471-39127-1.
- Glasstone, Sessionske. Nuclear Reactor Technology: Reactor System Technology, Springer; 4th edition, 1994, ISBN:978-0412985317
- WSC Williams. Nuclear and Particle Physics. Clarendon Press; 1st edition, 1991, ISBN:978-0198520467
- GR. stay in Physics of Nuclear Kinetics. Addison-Wesley Pub. Dog; 1st edition, 1965
- Robert Reed Burn, Introduction to Nuclear Reactor Operation, 1988.
- US Department of Energy, Nuclear Physics and Reactor Theory. DOE Fundamentals Manual, Volumes 1 & 2 January 1993.
- Paul Reuss, Neutron Physics. Computer Sciences, 2008. ISBN: 978-2759800414.
Advanced Reactor Physics:
- KO Ott, WA Bezella, Introductory Nuclear Reactor Statics, American Nuclear Society, revised edition (1989), 1989, ISBN: 0-894-48033-2
- KO Ott, R. J. Neuhold, Introductory Nuclear Reactor Dynamics, American Nuclear Society, 1985, ISBN: 0-894-48029-4.
- DL Hetrick, Dynamics of Nuclear Reactors, American Nuclear Society, 1993, ISBN: 0-894-48453-2.
- E.E. Lewis, W.F. Miller, Computational Methods of Neutron Transport, American Nuclear Society, 1993, ISBN: 0-894-48452-4.
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