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atomic number
atomic number often represented by the symbol Z, the number of protons in the nucleus of an atom , as well as the number of electrons in the neutral atom. Atoms with the same atomic number make up a chemical element . Atomic numbers were first assigned to the elements c.1913 by H. G. J. Moseley; he arranged the elements in an order based on certain characteristics of their X-ray spectra and then numbered them accordingly. The elements are now arranged in the periodic table in the order of their atomic numbers. Mendeleev's periodic law was originally based on atomic weights . See mass number . |
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"atomic number." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. "atomic number." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1E1-atomicnu.html "atomic number." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-atomicnu.html |
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atomic number
atomic number Chemical elements are composed of atoms, all of which are held together by electrical charges. Every atom has a relatively heavy nucleus that is composed of protons (with a positive charge) and neutrons (neutral particles). Orbiting the nucleus there are a number of exceptionally light electrons, whose negative charges balance the positive charge provided by the protons. The number of protons in the structure provides the atomic number; atoms having the same atomic number belong to the same chemical element.
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AILSA ALLABY and MICHAEL ALLABY. "atomic number." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. AILSA ALLABY and MICHAEL ALLABY. "atomic number." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O13-atomicnumber.html AILSA ALLABY and MICHAEL ALLABY. "atomic number." A Dictionary of Earth Sciences. 1999. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-atomicnumber.html |
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atomic number
atomic number (proton number) Number of protons in the nucleus of an atom of an element, which is equal to the number of electrons moving around that nucleus. It is abbreviated to ‘at.no.’ and represented by the symbol Z. The atomic number determines the chemical properties of an element and its position in the periodic table. Isotopes of an element all have the same atomic number but a different atomic mass number.
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"atomic number." World Encyclopedia. 2005. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. "atomic number." World Encyclopedia. 2005. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O142-atomicnumber.html "atomic number." World Encyclopedia. 2005. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-atomicnumber.html |
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