isotope

[ahy-suh-tohp]
noun Chemistry.
any of two or more forms of a chemical element, having the same number of protons in the nucleus, or the same atomic number, but having different numbers of neutrons in the nucleus, or different atomic weights. There are 275 isotopes of the 81 stable elements, in addition to over 800 radioactive isotopes, and every element has known isotopic forms. Isotopes of a single element possess almost identical properties.

Origin:
1910–15; iso- + -tope < Greek tópos place

isotopic [ahy-suh-top-ik] , adjective
isotopically, adverb
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source Link To isotopes
Collins
World English Dictionary
isotope (ˈaɪsəˌtəʊp)
 
n
one of two or more atoms with the same atomic number that contain different numbers of neutrons
 
[C20: from iso- + Greek topos place]
 
isotopic
 
adj
 
iso'topically
 
adv
 
isotopy
 
n

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
Cite This Source
Etymonline
Word Origin & History

isotope
1913, introduced by British chemist Frederick Soddy (1877-1956) on suggestion of Margaret Todd, from Gk. isos "equal" + topos "place;" so called because despite the different atomic weights, the various forms of an element occupy the same place on the periodic table.
Online Etymology Dictionary, © 2010 Douglas Harper
Cite This Source
American Heritage
Medical Dictionary

isotope i·so·tope (ī'sə-tōp')
n.
One of two or more atoms having the same atomic number but different mass numbers.


i'so·top'ic (-tŏp'ĭk) adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Cite This Source
American Heritage
Science Dictionary
isotope   (ī'sə-tōp')  Pronunciation Key 
One of two or more atoms that have the same atomic number (the same number of protons) but a different number of neutrons. Carbon 12, the most common form of carbon, has six protons and six neutrons, whereas carbon 14 has six protons and eight neutrons. Isotopes of a given element typically behave alike chemically. With the exception of hydrogen, elements found on Earth generally have the same number of protons and neutrons; heavier and lighter isotopes (with more or fewer neutrons) are often unstable and undergo radioactive decay.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
Cite This Source
American Heritage
Cultural Dictionary
isotope [(eye-suh-tohp)]

In physics, different forms of the same element, with nuclei that have the same number of protons but different numbers of neutrons. Isotopes are distinguished from each other by giving the combined number of protons and neutrons in the nucleus. For example, uranium 235 is the isotope of uranium that has 235 protons and neutrons in its nucleus rather than the more commonly occurring 238. All elements have isotopes.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
Cite This Source
Example sentences
Isotopes are versions of an element that have almost the same chemical
  properties but different atomic weights.
But the world has a short attention span, whereas the half-lives of many
  radioactive isotopes are long indeed.
Isotopes can even indicate the order in which the planets formed.
Oxygen isotopes from drinking water, for example, become fixed in people's
  teeth as they age.
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature