Browse Definitions :
Definition

isotope

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

Join the conversation

3 comments

Send me notifications when other members comment.

Please create a username to comment.

I have found a typo. It says neutron s instead of neutrons.
Cancel
This is not a typo but what should have been written was Neutron/s not neutron s in order to make it flow better

Cancel
It is not a typo or a way to make it flow better but because they need to hyperlink it to another page.
Cancel

SearchCompliance

  • risk assessment

    Risk assessment is the identification of hazards that could negatively impact an organization's ability to conduct business.

  • PCI DSS (Payment Card Industry Data Security Standard)

    The Payment Card Industry Data Security Standard (PCI DSS) is a widely accepted set of policies and procedures intended to ...

  • risk management

    Risk management is the process of identifying, assessing and controlling threats to an organization's capital and earnings.

SearchSecurity

  • tokenization

    Tokenization is the process of replacing sensitive data with unique identification symbols that retain all the essential ...

  • incident response

    Incident response is an organized approach to addressing and managing the aftermath of a security breach or cyberattack, also ...

  • Federal Information Security Management Act (FISMA)

    The Federal Information Security Management Act (FISMA) is United States legislation that defines a framework of guidelines and ...

SearchHealthIT

SearchDisasterRecovery

  • call tree

    A call tree is a layered hierarchical communication model that is used to notify specific individuals of an event and coordinate ...

  • Disaster Recovery as a Service (DRaaS)

    Disaster recovery as a service (DRaaS) is the replication and hosting of physical or virtual servers by a third party to provide ...

  • cloud disaster recovery (cloud DR)

    Cloud disaster recovery (cloud DR) is a combination of strategies and services intended to back up data, applications and other ...

SearchStorage

Close