Part of the Computing fundamentals glossary:

An isotope is a form of a chemical element whose atomic nucleus contains a specific number of neutron s, in addition to the number of proton s that uniquely defines the element. The nuclei of most atom s contain neutrons as well as protons. (An exception is the common form of hydrogen, whose nucleus consists of a lone proton.) Every chemical element has more than one isotope. For any element, one of the isotopes is more abundant in nature than any of the others, although often multiple isotopes of a single element are mixed.

The isotope of an element is defined by the nucleon number, which is the sum of the number of protons and the number of neutrons in the atomic nucleus. The nucleon number is customarily written as a superscript preceding the chemical symbol for the element. For example, 16 O represents oxygen-16, which has 8 protons and 8 neutrons, while 12 C represents carbon-12, with 6 protons and 6 neutrons. These are the most common naturally occurring isotopes of oxygen and carbon, respectively. Some carbon-14 is found in nature. An atom of carbon-14 contains 6 protons and 8 neutrons and is denoted 14 C. Over time, 14 C decays into 12 C.

Sometimes the isotope of an element is denoted by writing the nucleon number after the chemical symbol, and not as a superscript. Thus, some texts will denote carbon-14 as C-14 or C14 instead of 14 C.

Certain isotopes of elements are unstable, giving off ionizing radiation, also known as radioactivity. Such an isotope is called a radioisotope. Carbon-14 is a radioisotope of carbon. In the case of an element that is radioactive in all its known forms, such as uranium (U), certain isotopes are more radioactive than others, and/or give off different proportions of the various types of ionizing radiation.

This was last updated in September 2005
Posted by: Margaret Rouse

Related Terms

Definitions

  • disruptive technology

    - A disruptive technology is one that displaces an established technology and shakes up the industry. Harvard Business School professor Clayton M. Christensen coined the term.  In his 1997 best-sell... (WhatIs.com)

  • application program interface (API)

    - An application program interface (API) is code that allows two software programs to communicate with each other. Typically, APIs are released for third-party development as part of a software devel... (SearchExchange.com)

  • Microsoft Windows Control Panel

    - The Microsoft Windows Control Panel is a management tool for the Windows operating system (OS) that allows end users to change settings and manage tasks within the OS.  (SearchWindowsServer.com)

Glossaries

  • Computing fundamentals

    - Terms related to computer fundamentals, including computer hardware definitions and words and phrases about software, operating systems, peripherals and troubleshooting.

  • Internet applications

    - This WhatIs.com glossary contains terms related to Internet applications, including definitions about Software as a Service (SaaS) delivery models and words and phrases about web sites, e-commerce ...

Ask a Question. Find an Answer.Powered by ITKnowledgeExchange.com

Ask An IT Question

Get answers from your peers on your most technical challenges

Ask Question

Tech TalkComment

Share
Comments

    Results

    Contribute to the conversation

    All fields are required. Comments will appear at the bottom of the article.