Rutherford model
Overview
 
The Rutherford model or planetary model is a model of the atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...

 devised by Ernest Rutherford
Ernest Rutherford
Ernest Rutherford, 1st Baron Rutherford of Nelson OM, FRS was a New Zealand-born British chemist and physicist who became known as the father of nuclear physics...

. Rutherford directed the famous Geiger-Marsden experiment
Geiger-Marsden experiment
The Geiger–Marsden experiment was an experiment to probe the structure of the atom performed by Hans Geiger and Ernest Marsden in 1909, under the direction of Ernest Rutherford at the Physical Laboratories of the University of Manchester...

 in 1909, which suggested on Rutherford's 1911 analysis that the so-called "plum pudding model
Plum pudding model
The plum pudding model of the atom by J. J. Thomson, who discovered the electron in 1897, was proposed in 1904 before the discovery of the atomic nucleus. In this model, the atom is composed of electrons The plum pudding model of the atom by J. J. Thomson, who discovered the electron in 1897, was...

" of J. J. Thomson
J. J. Thomson
Sir Joseph John "J. J." Thomson, OM, FRS was a British physicist and Nobel laureate. He is credited for the discovery of the electron and of isotopes, and the invention of the mass spectrometer...

 of the atom was incorrect. Rutherford's new model for the atom, based on the experimental results, had the new features of a relatively high central charge concentrated into a very small volume in comparison to the rest of the atom and containing the bulk of the atomic mass
Atomic mass
The atomic mass is the mass of a specific isotope, most often expressed in unified atomic mass units. The atomic mass is the total mass of protons, neutrons and electrons in a single atom....

 (the nucleus
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...

 of the atom).

Rutherford's model did not make any new headway in explaining the electron-structure of the atom; in this regard Rutherford merely mentioned earlier atomic models in which a number of tiny electrons circled the nucleus like planets around the sun, or a ring around a planet (such as Saturn).
Encyclopedia
The Rutherford model or planetary model is a model of the atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...

 devised by Ernest Rutherford
Ernest Rutherford
Ernest Rutherford, 1st Baron Rutherford of Nelson OM, FRS was a New Zealand-born British chemist and physicist who became known as the father of nuclear physics...

. Rutherford directed the famous Geiger-Marsden experiment
Geiger-Marsden experiment
The Geiger–Marsden experiment was an experiment to probe the structure of the atom performed by Hans Geiger and Ernest Marsden in 1909, under the direction of Ernest Rutherford at the Physical Laboratories of the University of Manchester...

 in 1909, which suggested on Rutherford's 1911 analysis that the so-called "plum pudding model
Plum pudding model
The plum pudding model of the atom by J. J. Thomson, who discovered the electron in 1897, was proposed in 1904 before the discovery of the atomic nucleus. In this model, the atom is composed of electrons The plum pudding model of the atom by J. J. Thomson, who discovered the electron in 1897, was...

" of J. J. Thomson
J. J. Thomson
Sir Joseph John "J. J." Thomson, OM, FRS was a British physicist and Nobel laureate. He is credited for the discovery of the electron and of isotopes, and the invention of the mass spectrometer...

 of the atom was incorrect. Rutherford's new model for the atom, based on the experimental results, had the new features of a relatively high central charge concentrated into a very small volume in comparison to the rest of the atom and containing the bulk of the atomic mass
Atomic mass
The atomic mass is the mass of a specific isotope, most often expressed in unified atomic mass units. The atomic mass is the total mass of protons, neutrons and electrons in a single atom....

 (the nucleus
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...

 of the atom).

Rutherford's model did not make any new headway in explaining the electron-structure of the atom; in this regard Rutherford merely mentioned earlier atomic models in which a number of tiny electrons circled the nucleus like planets around the sun, or a ring around a planet (such as Saturn). However, by implication, Rutherford's concentration of most of the atom's mass into a very small core made a planetary model an even more likely metaphor than before, as such a core would contain most of the atom's mass, in an analogous way to the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 containing most of the solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

's mass. Rutherford's model was later corrected by Niels Bohr
Niels Bohr
Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...

.

Experimental basis for the model

In 1911, Rutherford came forth with his own physical model for subatomic structure, as an interpretation for the unexpected experimental results. In it, the atom is made up of a central charge (this is the modern atomic nucleus
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...

, though Rutherford did not use the term "nucleus" in his paper) surrounded by a cloud of (presumably) orbiting electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

s. In this May 1911 paper, Rutherford only commits himself to a small central region of very high positive or negative charge in the atom.
"For concreteness, consider the passage of a high speed α particle
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...

 through an atom having a positive central charge N e
Elementary charge
The elementary charge, usually denoted as e, is the electric charge carried by a single proton, or equivalently, the absolute value of the electric charge carried by a single electron. This elementary charge is a fundamental physical constant. To avoid confusion over its sign, e is sometimes called...

, and surrounded by a compensating charge of N electrons."



From purely energetic considerations of how far particles of known speed would be able to penetrate toward a central charge of 100 e, Rutherford was able to calculate that the radius of his gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 central charge would need to be less (how much less could not be told) than 3.4 x (the modern value is only about a fifth of this). This was in a gold atom known to be 10−10 metres or so in radius—a very surprising finding, as it implied a strong central charge less than 1/3000th of the diameter of the atom.

The Rutherford model served to concentrate a great deal of the atom's charge and mass to a very small core, but didn't attribute any structure to the remaining electrons and remaining atomic mass. It did mention the atomic model of Hantaro Nagaoka, in which the electrons are arranged in one or more rings, with the specific metaphorical structure of the stable rings of Saturn. The so-called plum pudding model
Plum pudding model
The plum pudding model of the atom by J. J. Thomson, who discovered the electron in 1897, was proposed in 1904 before the discovery of the atomic nucleus. In this model, the atom is composed of electrons The plum pudding model of the atom by J. J. Thomson, who discovered the electron in 1897, was...

 of J.J. Thomson had also had rings of orbiting electrons.

The Rutherford paper suggested that the central charge of an atom might be "proportional" to its atomic mass in hydrogen mass units
Atomic mass unit
The unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...

 u (roughly 1/2 of it, in Rutherford's model). For gold, this mass number is 197 (not then known to great accuracy) and was therefore modeled by Rutherford to be possibly 196 u. However, Rutherford did not attempt to make the direct connection of central charge to atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...

, since gold's place on the periodic table
Periodic table
The periodic table of the chemical elements is a tabular display of the 118 known chemical elements organized by selected properties of their atomic structures. Elements are presented by increasing atomic number, the number of protons in an atom's atomic nucleus...

 was known to be about 79 u, and gold's "atomic number" (at that time merely its place number in the periodic table) that Rutherford did not formally suggest the two numbers (atomic number and nuclear charge) might be exactly the same.

A month after Rutherford's paper appeared, the proposal regarding the exact identity of atomic number and nuclear charge was made by Antonius van den Broek
Antonius Van den Broek
Antonius Johannes van den Broek was a Dutch amateur physicist notable for being the first who realized that the number of an element in the periodic table corresponds to the charge of its atomic nucleus....

, and later confirmed experimentally within two years, by Henry Moseley
Henry Moseley
Henry Gwyn Jeffreys Moseley was an English physicist. Moseley's outstanding contribution to the science of physics was the justification from physical laws of the previous empirical and chemical concept of the atomic number. This stemmed from his development of Moseley's law in X-ray spectra...

.

To sum up the Ruthford Experiment. It proved that was a soild.

Key points

  • The electron cloud
    Atomic orbital
    An atomic orbital is a mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus...

     of the atom does not influence alpha particle scattering
    Rutherford scattering
    In physics, Rutherford scattering is a phenomenon that was explained by Ernest Rutherford in 1911, and led to the development of the Rutherford model of the atom, and eventually to the Bohr model. It is now exploited by the materials analytical technique Rutherford backscattering...

    .
  • Much of an atom's charge (specifically, its positive charge) is concentrated in a relatively tiny volume at the center of the atom, known today as the nucleus. The magnitude of this charge is proportional to (up to a charge number that can be approximately half of) the atom's atomic mass
    Atomic mass
    The atomic mass is the mass of a specific isotope, most often expressed in unified atomic mass units. The atomic mass is the total mass of protons, neutrons and electrons in a single atom....

     - the remaining mass is now known to be mostly attributed to neutrons. This concentrated central mass and charge is responsible for deflecting both alpha and beta
    Beta particle
    Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay...

     particles.
  • The mass of heavy atoms such as gold is mostly concentrated in the central charge region, since calculations show it is not deflected or moved by the high speed alpha particles, which have very high momentum
    Momentum
    In classical mechanics, linear momentum or translational momentum is the product of the mass and velocity of an object...

     in comparison to electrons, but not with regard to a heavy atom as a whole.

Contribution to modern science

After Rutherford's discovery, scientists started to realize that the atom is not ultimately a single particle, but is made up of far smaller subatomic particles. Following research was done to figure out the exact atomic structure which led to Rutherford’s gold foil experiment
Geiger-Marsden experiment
The Geiger–Marsden experiment was an experiment to probe the structure of the atom performed by Hans Geiger and Ernest Marsden in 1909, under the direction of Ernest Rutherford at the Physical Laboratories of the University of Manchester...

. They eventually discovered that atoms have a positively-charged nucleus (with an exact atomic number of charges) in the center, with a radius of about 1.2 x 10−15 meters x [Atomic Mass Number]1/3. Since electrons were found to be even smaller, this meant that the atom consists of mostly empty space.

Later on, scientists found the expected number of electrons (the same as the atomic number) in an atom by using X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

s. When an X-ray passes through an atom, some of it is scattered
Scattering
Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of...

, while the rest passes through the atom. Since the X-ray loses its intensity primarily due to scattering at electrons, by noting the rate of decrease in X-ray intensity, the number of electrons contained in an atom can be accurately estimated.

Symbolism

Despite its inaccuracy, the Rutherford model caught the imagination of the public in a way that the more correct Bohr model
Bohr model
In atomic physics, the Bohr model, introduced by Niels Bohr in 1913, depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the solar system, but with electrostatic forces providing attraction,...

 did not, and has continually been used as a symbol for atoms and atomic energy. Examples of its use over the past century include:
  • The logo of the United States Atomic Energy Commission
    United States Atomic Energy Commission
    The United States Atomic Energy Commission was an agency of the United States government established after World War II by Congress to foster and control the peace time development of atomic science and technology. President Harry S...

    , which was in part responsible for its later usage in relation to nuclear fission
    Nuclear fission
    In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...

     technology in particular.
  • The flag of the International Atomic Energy Agency
    International Atomic Energy Agency
    The International Atomic Energy Agency is an international organization that seeks to promote the peaceful use of nuclear energy, and to inhibit its use for any military purpose, including nuclear weapons. The IAEA was established as an autonomous organization on 29 July 1957...

     is a Rutherford atom, enclosed in olive
    Olive
    The olive , Olea europaea), is a species of a small tree in the family Oleaceae, native to the coastal areas of the eastern Mediterranean Basin as well as northern Iran at the south end of the Caspian Sea.Its fruit, also called the olive, is of major agricultural importance in the...

     branches.
  • The US minor league baseball
    Minor league baseball
    Minor league baseball is a hierarchy of professional baseball leagues in the Americas that compete at levels below Major League Baseball and provide opportunities for player development. All of the minor leagues are operated as independent businesses...

     Albuquerque Isotopes
    Albuquerque Isotopes
    The Albuquerque Isotopes are a minor league baseball team based in Albuquerque, New Mexico. The team, which plays in the Pacific Coast League, is the Triple-A affiliate of the Los Angeles Dodgers...

    ' logo is a Rutherford atom, with the electron orbits forming an A.
  • The Unicode
    Unicode
    Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...

     Miscellaneous Symbols
    Miscellaneous Symbols
    The Miscellaneous Symbols Unicode block contains various glyphs representing things from a variety of categories: Astrological, Astronomical, Chess, Dice, Ideological symbols, Musical notation, Political symbols, Recycling, Religious symbols, Trigrams, Warning signs and Weather.-Tables:Note: These...

     codepoint U+269B (⚛) uses a Rutherford atom.
  • On maps, it is generally used to indicate a nuclear power
    Nuclear power
    Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...

     installation.
  • The Atomic whirl
    Atomic whirl
    The atomic whirl is the logo of the American Atheists, and has come to be used as a symbol of atheism in general.The Atomic Whirl is based on the well known Rutherford Atom, showing the orbital paths of electrons around the central nucleus...

    , symbol of American Atheists
    American Atheists
    American Atheists is an organization in the United States dedicated to defending the civil liberties of atheists and advocating for the complete separation of church and state. It provides speakers for colleges, universities, clubs and the news media. It also publishes books and the monthly...

    , incorporates the design of a Rutherford atom.
  • The symbols of "atomic powered" superhero
    Superhero
    A superhero is a type of stock character, possessing "extraordinary or superhuman powers", dedicated to protecting the public. Since the debut of the prototypical superhero Superman in 1938, stories of superheroes — ranging from brief episodic adventures to continuing years-long sagas —...

    es, such as Captain Atom
    Captain Atom
    Captain Atom is a fictional comic book superhero that has existed in three basic incarnations. Created by writer Joe Gill and artist/co-writer Steve Ditko, he first appeared in Space Adventures #33 . Captain Atom was created for Charlton Comics but was later acquired by DC Comics and revised for...

     and Nuklon.
  • It is used between the change of scenes of the show The Big Bang Theory
    The Big Bang Theory
    The Big Bang Theory is an American sitcom created by Chuck Lorre and Bill Prady, both of whom serve as executive producers on the show, along with Steven Molaro. All three also serve as head writers...

    .
  • In the show The Adventures of Jimmy Neutron: Boy Genius
    The Adventures of Jimmy Neutron: Boy Genius
    The Adventures of Jimmy Neutron: Boy Genius, often shortened to just Jimmy Neutron, is an American animated television series, and spin-off of the Academy Award-nominated computer-animated movie, Jimmy Neutron: Boy Genius. The series first officially aired on July 20, 2002, on Nickelodeon...

    , the Rutherford atom is seen in scene transitions, and all throughout Jimmy's lab.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK