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Encyclopedia > Alpha particle
An alpha particle is deflected by a magnetic field
An alpha particle is deflected by a magnetic field
Alpha radiation consists of helium-4 nuclei and is readily stopped by a sheet of paper. Beta radiation, consisting of electrons, is halted by an aluminium plate. Gamma radiation is eventually absorbed as it penetrates a dense material.
Alpha radiation consists of helium-4 nuclei and is readily stopped by a sheet of paper. Beta radiation, consisting of electrons, is halted by an aluminium plate. Gamma radiation is eventually absorbed as it penetrates a dense material.
Alpha decay
Alpha decay

Alpha particles (named after and denoted by the first letter in the Greek alphabet, α) consist of two protons and two neutrons bound together into a particle identical to a helium nucleus; hence, it can be written as He2+ or 42He. They are a highly ionizing form of particle radiation, and have low penetration. The alpha particle mass is 6.644656×10-27 kg, which is equivalent to the energy of 3.72738 GeV. The charge of an alpha particle is equal to +2e, where e is the magnitude of charge on an electron, e=1.602176462x10-19C. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Image File history File links Alfa_beta_gamma_radiation. ... Image File history File links Alfa_beta_gamma_radiation. ... Helium-4 is a non-radioactive and light isotope of helium. ... For other uses, see Electron (disambiguation). ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... The Greek alphabet (Greek: ) is an alphabet consisting of 24 letters that has been used to write the Greek language since the late 8th or early 9th century BC. It was the first alphabet in the narrow sense, that is, a writing system using a separate symbol for each vowel... For other uses, see Proton (disambiguation). ... This article or section does not adequately cite its references or sources. ... For other uses, see Helium (disambiguation). ... Radiation hazard symbol. ... Particle radiation is the radiation of energy by means of small fast-moving particles that have energy and mass. ... Look up giga- in Wiktionary, the free dictionary. ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ...


Alpha particles are emitted by radioactive nuclei such as uranium or radium in a process known as alpha decay. This sometimes leaves the nucleus in an excited state, with the emission of a gamma ray removing the excess energy. In contrast to beta decay, alpha decay is mediated by the strong nuclear force. Classically, alpha particles do not have enough energy to escape the potential of the nucleus. However, the quantum tunnelling effect allows them to escape. Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ... General Name, symbol, number uranium, U, 92 Chemical series actinides Group, period, block n/a, 7, f Appearance silvery gray metallic; corrodes to a spalling black oxide coat in air Standard atomic weight 238. ... General Name, Symbol, Number radium, Ra, 88 Chemical series alkaline earth metals Group, Period, Block 2, 7, s Appearance silvery white metallic Standard atomic weight (226) g·mol−1 Electron configuration [Rn] 7s2 Electrons per shell 2, 8, 18, 32, 18, 8, 2 Physical properties Phase solid Density (near r. ... Alpha decay Alpha decay is a type of radioactive decay in which an atom emits an alpha particle (two protons and two neutrons bound together into a particle identical to a helium nucleus) and transforms (or decays) into an atom with a mass number 4 less and atomic number 2... This article is about electromagnetic radiation. ... In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ... The strong nuclear force or strong interaction (also called color force or colour force) is a fundamental force of nature which affects only quarks and antiquarks, and is mediated by gluons in a similar fashion to how the electromagnetic force is mediated by photons. ... Quantum tunneling is the quantum-mechanical effect of transitioning through a classically-forbidden energy state. ...


When an alpha particle is emitted, the atomic mass of an element goes down by roughly 4.0015 u, due to the loss of 2 neutrons and 2 protons. The atomic number of the atom goes down by 2, as a result of the loss of 2 protons; the atom becomes a new element. An example of this is when radium becomes radon gas due to alpha decay. The atomic mass (ma) is the mass of an atom at rest, most often expressed in unified atomic mass units. ... The atomic mass unit (amu), unified atomic mass unit (u), or dalton (Da), is a small unit of mass used to express atomic masses and molecular masses. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 940 MeV/c² (1. ... See also: List of elements by atomic number In chemistry and physics, the atomic number (also known as the proton number) is the number of protons found in the nucleus of an atom. ... For other uses, see Radon (disambiguation). ...


The energy of alpha particles varies, with higher energy alpha particles being emitted from larger nuclei, but most alpha particles have energies of between 3 and 7 MeV. This is a substantial amount of energy for a single particle, but their high mass means alpha particles have a lower speed (with a typical kinetic energy of 5 MeV the speed is 15,000 km/s) than any other common type of radiation (β particles, γ rays, neutrons, etc). Because of their charge and large mass, alpha particles are easily absorbed by materials and can travel only a few centimeters in air. They can be absorbed by tissue paper or the outer layers of human skin (about 40 micrometres, equivalent to a few cells deep) and so are not generally dangerous to life unless the source is ingested or inhaled. Because of this high mass and strong absorption, however, if alpha radiation does enter the body (most often because radioactive material has been inhaled or ingested), it is the most destructive form of ionizing radiation. It is the most strongly ionizing, and with large enough doses can cause any or all of the symptoms of radiation poisoning. It is estimated that chromosome damage from alpha particles is about 100 times greater than that caused by an equivalent amount of other radiation. The alpha emitter polonium-210 is suspected of playing a role in lung and bladder cancer related to tobacco smoking. Alpha radiation consists of helium nuclei and is readily stopped by a sheet of paper. ... This article is about electromagnetic radiation. ... Neutron radiation consists of free neutrons. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the diameter of a droplet of mist or fog. ... Radiation hazard symbol. ... Radiation poisoning, also called radiation sickness, is a form of damage to organ tissue due to excessive exposure to ionizing radiation. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... Polonium-210 is the most readily available isotope of Polonium. ... Lung cancer is the malignant transformation and expansion of lung tissue, and is the most lethal of all cancers worldwide, responsible for 1. ... Bladder cancer refers to any of several types of malignant growths of the urinary bladder. ... The cigarette is the most common method of smoking tobacco. ...


Most smoke detectors contain a small amount of the alpha emitter americium-241. This isotope is extremely dangerous if inhaled or ingested, but the danger is minimal if the source is kept sealed. Many municipalities have established programs to collect and dispose of old smoke detectors, rather than let them go into the general waste stream. A smoke detector or smoke alarm is a device that detects smoke and issues an alarm to alert nearby people that there is a potential fire. ... General Name, Symbol, Number americium, Am, 95 Chemical series actinides Group, Period, Block n/a, 7, f Appearance silvery white Atomic mass (243) g/mol Electron configuration [Rn] 5f7 7s2 Electrons per shell 2, 8, 18, 32, 25, 8, 2 Physical properties Phase solid Density (near r. ...


Because alpha particles occur naturally, but can have energy high enough to participate in a nuclear reaction, study of them led to much early knowledge of nuclear physics. The physicist Ernest Rutherford famously used alpha particles to infer that J. J. Thomson's Plum pudding model of the atom was fundamentally flawed. Rutherford's famous gold foil experiment was conducted by his students Hans Geiger and Ernest Marsden. A narrow beam of alpha particles was set up, passing through very thin (only a few hundred atoms thick) gold foil. The alpha particles were detected by a zinc sulfide screen, which emits a flash of light upon an alpha particle collision. Rutherford hypothesisized that, assuming the "plum pudding" model of the atom was correct, the positively charged alpha particles would be only slightly deflected, if at all, by the dispersed positive charge predicted. It was found that some of the alpha particles were deflected at much larger angles than expected, with some even bouncing back. Although most of the alpha particles went straight through as expected, Rutherford commented that the few particles that were deflected was akin to shooting a fifteen inch shell at tissue paper only to have it bounce off, again assuming the "plum pudding" theory was correct. It was soon determined that the positive charge of the atom was concentrated in a small area in the center of the atom, hence making the positive charge dense enough to deflect any positively charged alpha particles that happened to come close to what was later termed the nucleus (it was not known at the time that alpha particles were themselves nuclei nor was the existence of protons or neutrons known). Rutherford's experiment subsequently led to the Bohr model and later the modern wave-mechanical model of the atom. In nuclear physics, a nuclear reaction is a process in which two nuclei or nuclear particles collide to produce products different from the initial particles. ... Nuclear physics is the branch of physics concerned with the nucleus of the atom. ... Ernest Rutherford, 1st Baron Rutherford of Nelson OM PC FRS (30 August 1871 - 19 October 1937), widely referred to as Lord Rutherford, was a nuclear physicist who became known as the father of nuclear physics. ... Sir Joseph John “J.J.” Thomson, OM, FRS (18 December 1856 – 30 August 1940) was a British physicist and Nobel laureate, credited for the discovery of the electron and of isotopes, and the invention of the mass spectrometer. ... A schematic representation of the plum pudding model of the atom. ... Johannes (Hans) Wilhelm Geiger (September 30, 1882 – September 24, 1945) was a German physicist. ... Sir Ernest Marsden (1888 - 1970), was a British-New Zealand physicist. ... Zinc sulfide (or zinc sulphide) is a chemical compound with the formula ZnS. Zinc sulfide is a white to yellow colored powder or crystal. ... Niels Henrik David Bohr (October 7, 1885 – November 18, 1962) was a Danish physicist who made fundamental contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in 1922. ... The Bohr model of the hydrogen atom, where negatively charged electrons confined to atomic shells encircle a small positively charged atomic nucleus, and that an electron jump between orbits must be accompanied by an emitted or absorbed amount of electromagnetic energy hν. The orbits that the electrons travel in are...


Rutherford's work also improved on previous measurements of the ratio of an alpha particle's mass to charge, allowing him to deduce that alpha particles were helium nuclei.[1]


In computer technology, DRAM 'soft errors' were linked to alpha particles in 1978 in Intel's DRAM chips. The discovery led to strict control of radioactive elements in the packaging of semiconductor materials, and the problem was largely considered 'solved'. Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. ... In electronics and computing, an error is a signal or datum which is wrong. ... Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ...


See also

Wikimedia Commons has media related to:
Alpha particle

Image File history File links Commons-logo. ... Alpha radiation consists of helium nuclei and is readily stopped by a sheet of paper. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... At least the following radioactive materials are known to emit alpha particles. ... Nuclear physics is the branch of physics concerned with the nucleus of the atom. ... Thousands of particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... Radioactivity may mean: Look up radioactivity in Wiktionary, the free dictionary. ... A radionuclide is an atom with an unstable nucleus. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... This article is about electromagnetic radiation. ... It has been suggested that this article or section be merged with delta ray. ... Epsilon Radiation is tertiary radiation caused by secondary radiation. ...

References

  1. ^ Hellemans, Alexander; Bryan Bunch (1988). The Timetables of Science. New York, New York: Simon and Schuster, 411. ISBN 0671621300. 
  • Tipler, Paul; Llewellyn, Ralph (2002). Modern Physics (4th ed.). W. H. Freeman. ISBN 0-7167-4345-0. 

  Results from FactBites:
 
Alpha particle - Wikipedia, the free encyclopedia (769 words)
Alpha particles or alpha rays (named after the first letter in the greek alphabet, α) are a highly ionizing form of particle radiation which have low penetration.
When an alpha particle is emitted, the atomic mass of an element goes down by roughly 4 amu, due to the loss of 4 nucleons.
The physicist Ernest Rutherford famously used alpha particles to infer that Lord Kelvin's "plum pudding" model of the atom was fundamentally flawed.
Alpha Decay (268 words)
In alpha decay, the atomic number changes, so the original (or parent) atoms and the decay-product (or daughter) atoms are different elements and therefore have different chemical properties.
In the alpha decay of a nucleus, the change in binding energy appears as the kinetic energy of the alpha particle and the daughter nucleus.
Because this energy must be shared between these two particles, and because the alpha particle and daughter nucleus must have equal and opposite momenta, the emitted alpha particle and recoiling nucleus will each have a well-defined energy after the decay.
  More results at FactBites »

 
 

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