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.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with atoms
Fujitsu Develops Technology for Low-Temperature Full-Service Direct Formation of Graphene Transistors on Large-Scale Sub
Nov 27, 2009 |
5 / 5 (18) |
3
Fujitsu Laboratories today announced, as a world first, the development of a novel technology for forming graphene transistors directly on the entire surface of large-scale insulating substrates at low temperatures ...
Plasma produces KO cocktail for MRSA
Nov 26, 2009 |
4.9 / 5 (13) |
2
MRSA (methicillin-resistant Staphylococcus Aureus) and other drug-resistant bacteria could face annihilation as low-temperature plasma prototype devices have been developed to offer safe, quick, easy and un ...
Multiferroic compounds used to produce smaller and cheaper digital memories
Nov 27, 2009 |
4.6 / 5 (5) |
1
(PhysOrg.com) -- Is it possible to make even more compact digital memories for portable electronic devices and which consume even less energy? A team of French researchers has recently demonstrated that it ...
Herschel takes a peek at the ingredients of the galaxies
Nov 27, 2009 |
4.8 / 5 (9) |
1
(PhysOrg.com) -- The European Space Agency has today released spectacular new observations from the Herschel Space Observatory, including the UK-led SPIRE instrument. Spectrometers on board all three Hershel ...
Search results for atoms
New hydrogen-storage method discovered
Nov 22, 2009 |
4.3 / 5 (42) |
15
Scientists at the Carnegie Institution have found for the first time that high pressure can be used to make a unique hydrogen-storage material. The discovery paves the way for an entirely new way to approach ...
First atoms reported smashed in Large Hadron Collider (Update)
Nov 23, 2009 |
4.6 / 5 (37) |
26
Two circulating beams on Monday produced the first particle collisions in the world's biggest atom smasher, the Large Hadron Collider (LHC), three days after its restart, scientists announced.
Research sheds light on workings of anti-cancer drug
Chemistry / Analytical Chemistry
Nov 26, 2009 |
not rated yet |
0
(PhysOrg.com) -- The copper sequestering drug tetrathiomolybdate (TM) has been shown in studies to be effective in the treatment of Wilson disease, a disease caused by an overload of copper, and certain metastatic cancers. ...
Cells defend themselves from viruses, bacteria with armor of protein errors
Nov 25, 2009 |
5 / 5 (7) |
1
When cells are confronted with an invading virus or bacteria or exposed to an irritating chemical, they protect themselves by going off their DNA recipe and inserting the wrong amino acid into new proteins to defend them ...
Computational microscope peers into the working ribosome (w/ Video)
Nov 23, 2009 |
4.9 / 5 (9) |
2
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 ...
List of search results for atoms
