Atom
hideThe atom is a basic unit of matter consisting 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 (except in the case of hydrogen-1, which is the only stable nuclide with no neutron). The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain bound to each other, forming a molecule. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it has a positive or negative charge and is an ion. An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons determines the chemical element, and the number of neutrons determine the isotope of the element.
The name atom comes from the Greek ἄτομος/átomos, α-τεμνω, which means uncuttable, something that cannot be divided further. The concept of an atom as an indivisible component of matter was first proposed by early Indian and Greek philosophers. In the 17th and 18th centuries, chemists provided a physical basis for this idea by showing that certain substances could not be further broken down by chemical methods. During the late 19th and early 20th centuries, physicists discovered subatomic components and structure inside the atom, thereby demonstrating that the 'atom' was divisible. The principles of quantum mechanics were used to successfully model the atom.
Relative to everyday experience, atoms are minuscule objects with proportionately tiny masses. Atoms can only be observed individually using special instruments such as the scanning tunneling microscope. Over 99.9% of an atom's mass is concentrated in the nucleus, with protons and neutrons having roughly equal mass. Each element has at least one isotope with unstable nuclei that can undergo radioactive decay. This can result in a transmutation that changes the number of protons or neutrons in a nucleus. Electrons that are bound to atoms possess a set of stable energy levels, or orbitals, and can undergo transitions between them by absorbing or emitting photons that match the energy differences between the levels. The electrons determine the chemical properties of an element, and strongly influence an atom's magnetic properties.
For more information about Atom, read the full article at
Wikipedia.
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News tagged with atomic structure
Bacterial protein mimics its host to disable a key enzyme (w/ Video)
Dec 11, 2009 |
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(PhysOrg.com) -- Bacteria use all sorts of cunning to trick hosts into doing their bidding. One con in their bag of tricks: the molecular mimic. In this ruse, bacteria or their agents look for all purposes like some native ...
Absorbing Hydrogen Fluoride Gas to Enhance Crystal Growth
Dec 10, 2009 |
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(PhysOrg.com) -- Two scientists at the U.S. Department of Energy's Brookhaven National Laboratory have developed a method to control the buildup of hydrogen fluoride gas during the growth of precision crystals ...
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A little magic provides an atomic-level look at bone
Chemistry / Analytical Chemistry
Dec 02, 2009 |
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(PhysOrg.com) -- A new study using solid-state NMR spectroscopy to analyze intact bone paves the way for atomic-level explorations of how disease and aging affect bone. The research by scientists at the University of Michigan ...
Geneticist reveals molecular view of key epigenetic regulator
Dec 09, 2009 |
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In a paper published this week in the journal Proceedings of the National Academy of Sciences, Dr. Michael Kobor reported the structure and function of a key player in regulating chromatin in yeast and humans.
Researchers put a new spin on atomic musical chairs
Dec 02, 2009 |
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Researchers from the National Institute of Standards and Technology and the Naval Research Laboratory have developed a new way to introduce magnetic impurities in a semiconductor crystal by prodding it with ...
Caltech scientists film photons with electrons
Dec 16, 2009 |
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(PhysOrg.com) -- Techniques recently invented by researchers at the California Institute of Technology -- which allow the real-time, real-space visualization of fleeting changes in the structure of nanoscale ...
Watching Proteins Direct Crystal Growth One Step at a Time (w/ Video)
Dec 16, 2009 |
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(PhysOrg.com) -- Scientists at Berkeley Lab's Molecular Foundry imaged the growth of protein-studded mineral surfaces with unprecedented resolution and provided a glimpse into how living systems engineer key ...
The hidden lives of proteins
Dec 02, 2009 |
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An important Brandeis study appearing in the December 3 issue of Nature raises the curtain on the hidden lives of proteins at the atomic level. The study reports that for the first time, researchers used x ...
Computational microscope peers into the working ribosome (w/ Video)
Nov 23, 2009 |
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Two new studies reveal in unprecedented detail how the ribosome interacts with other molecules to assemble new proteins and guide them toward their destination in biological cells. The studies used molecular ...
Nanowires key to future transistors, electronics
Nov 26, 2009 |
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(PhysOrg.com) -- A new generation of ultrasmall transistors and more powerful computer chips using tiny structures called semiconducting nanowires are closer to reality after a key discovery by researchers ...
Peptides control crystal growth with 'switches, throttles and brakes'
Nanotechnology / Bio & Medicine
Nov 23, 2009 |
4.8 / 5 (5) |
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(PhysOrg.com) -- By producing some of the highest resolution images of peptides attaching to mineral surfaces, scientists have a deeper understanding how biomolecules manipulate the growth crystals. This research ...
New structure could produce efficient semiconductor laser sources
Dec 14, 2009 |
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(PhysOrg.com) -- University of Wisconsin-Madison researchers have achieved a nanoscale laser structure they anticipate will produce semiconductor lasers in the next two years that are more than twice as efficient ...
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