Browse Definitions:
Definition

atomic mass unit (AMU or amu)

An atomic mass unit (symbolized AMU or amu) is defined as precisely 1/12 the mass of an atom of carbon-12. The carbon-12 (C-12) atom has six protons and six neutrons in its nucleus.

In imprecise terms, one AMU is the average of the proton rest mass and the neutron rest mass. This is approximately 1.67377 x 10 -27 kilogram (kg), or 1.67377 x 10 -24 gram (g). The mass of an atom in AMU is roughly equal to the sum of the number of protons and neutrons in the nucleus.

The AMU is used to express the relative masses of, and thereby differentiate between, various isotopes of elements. Thus, for example, uranium-235 (U-235) has an AMU of approximately 235, while uranium-238 (U-238) is slightly more massive. The difference results from the fact that U-238, the most abundant naturally occurring isotope of uranium, has three more neutrons than U-235, an isotope that has been used in nuclear reactors and atomic bombs.

Also see our Table of Physical Units and Constants.

This was last updated in January 2011

Join the conversation

5 comments

Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.

please I want to know why it was the carbon atom ?
why it was not another atom , i.e. why it was not 1/23 from sodium nuclide weight is not it equal to 1/12 from carbon nuclide weight ???
Cancel
Share please I want to know why it was the carbon atom ?
why it was not another atom , i.e. why it was not 1/23 from sodium nuclide weight is not it equal to 1/12 from carbon nuclide weight ???
your comment
Cancel
How the scientist of that time know the mass of the carbon atom and they why choice this atom
Cancel
Share your commentHow the scientist of that time know the mass of the carbon atom and they why choice this atomWhy is it that when I try to research on the internet about," how to remove a proton from the nucleus of an atom nothing useful pops up. I just want knowledge not people thinking they know what their talking about. I know that you have to use gamma radiation an that ejecting a particle with gamma particle an changing an element is the way you do this process. But I'm seriously not seeing the scientific research an data to explain how this process works or is engineered. I'm sure that someone can explain to me nuclear and molecular physics for free but how when u work all the time and have kids an can't do your dream. Anyways sorry for rumbling an can someone please help me with finding a way to eject a proton from the nucleus without using a freaking gamma ray gun and hoping for a new element because that's what it feels like all I can find on the web is. A bunch of b.s..
Cancel
Why is it that when I try to research on the internet about," how to remove a proton from the nucleus of an atom nothing useful pops up. I just want knowledge not people thinking they know what their talking about. I know that you have to use gamma radiation an that ejecting a particle with gamma particle an changing an element is the way you do this process. But I'm seriously not seeing the scientific research an data to explain how this process works or is engineered. I'm sure that someone can explain to me nuclear and molecular physics for free but how when u work all the time and have kids an can't do your dream. Anyways sorry for rumbling an can someone please help me with finding a way to eject a proton from the nucleus without using a freaking gamma ray gun and hoping for a new element because that's what it feels like all I can find on the web is. A bunch of b.s..
Cancel

-ADS BY GOOGLE

File Extensions and File Formats

Powered by:

SearchCompliance

  • cyborg anthropologist

    A cyborg anthropologist is an individual who studies the interaction between humans and technology, observing how technology can ...

  • RegTech

    RegTech, or regulatory technology, is a term used to describe technology that is used to help streamline the process of ...

  • conduct risk

    Conduct risk is the prospect of financial loss to an organization that is caused by the actions of an organization's ...

SearchSecurity

  • security

    Security, in information technology (IT), is the defense of digital information and IT assets against internal and external, ...

  • insider threat

    An insider threat is a malicious hacker (also called a cracker or a black hat) who is an employee or officer of a business, ...

  • virus (computer virus)

    A computer virus is malicious code that replicates by copying itself to another program, computer boot sector or document.

SearchHealthIT

  • HIPAA Privacy Rule

    The Standards for Privacy of Individually Identifiable Health Information, commonly known as the HIPAA Privacy Rule, establishes ...

  • HIPAA business associate agreement (BAA)

    Under the U.S. Health Insurance Portability and Accountability Act of 1996, a HIPAA business associate agreement (BAA) is a ...

  • telemedicine

    Telemedicine is the remote delivery of healthcare services, such as health assessments or consultations, over the ...

SearchDisasterRecovery

  • data recovery

    Data recovery restores data that has been lost, accidentally deleted, corrupted or made inaccessible. Learn how data recovery ...

  • disaster recovery plan (DRP)

    A company's disaster recovery policy is enhanced with a documented DR plan that formulates strategies, and outlines preparation ...

  • fault-tolerant

    Systems with integrated fault tolerance are designed to withstand multiple hardware failures to ensure continuous availability.

SearchStorage

  • Secure Digital card (SD card)

    SD cards use flash memory to provide nonvolatile storage. They are more rugged than traditional storage media and are used in ...

  • data storage

    In a computer, storage is the place where data is held in an electromagnetic or optical form for access by a computer processor.

  • flash storage

    Flash-based storage, based on flash memory, is used for data repositories, storage systems and consumer devices, such as USB ...

SearchSolidStateStorage

  • flash file system

    Flash file systems are designed specifically for memory devices. A well-designed flash device and flash file system ensure ...

  • IOPS (input/output operations per second)

    IOPS measures the maximum number of reads and writes to non-contiguous storage. It is not an actual benchmark since vendor ...

  • eMMC (embedded MultiMediaCard)

    An embedded MultiMediaCard (eMMC) is a small storage device made up of NAND flash memory and a simple storage controller.

SearchCloudStorage

  • RESTful API

    A RESTful application program interface breaks down a transaction to create a series of small modules, each of which addresses an...

  • cloud storage infrastructure

    Cloud storage infrastructure is the hardware and software framework that supports the computing requirements of a private or ...

  • Zadara VPSA and ZIOS

    Zadara Storage provides block, file or object storage with varying levels of compute and capacity through its ZIOS and VPSA ...

Close