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1789 views
08:22 Sep-24-2008
Nandesh
how mass is reduced as isotope decays?

Hi,

How the mass of an isotope like Ir-192 is reduced as the isotope decays?


 
06:28 Sep-25-2008

S.R.G.PRABHU

Consultant, AUT specialist
FREELANCE,
India,
Joined Aug 2008
63
Re: how mass is reduced as isotope decays?
The decay of a radioactive isotope is nothing but emission of alpha, beta and gamma rays. Alpha rays consists of helium atoms. Each helium atom emitted will contribute to the decrease in atomic number by two, because atomic number of helium is 2.Hence radioactive decay leads to decrease in mass of the isotope.


----------- Start Original Message -----------
: Hi,
: How the mass of an isotope like Ir-192 is reduced as the isotope decays?
------------ End Original Message ------------




 
09:05 Sep-26-2008

S.V.Swamy

Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex ,
India,
Joined Feb 2001
784
Re: how mass is reduced as isotope decays? Dear Prabhu,

That was a good explanation but alpha rays are Helium nuclei, not atoms. Atoms are electrically neutral and have electrons to neutralise the positive charge of the nucleus. Since most of the mass is accounted by the nucleus, the mass of the atom and the mass of the nucleus can be taken as same in many situations. Beta particles are electrons emitted by the nucleus and theoretically there is a small loss of mass but for all practical purposes, the same is ignored. Gamma rays are photons of electromagnetic radiation and have no mass.

Regards.

Swamy

----------- Start Original Message -----------
:
: The decay of a radioactive isotope is nothing but emission of alpha, beta and gamma rays. Alpha rays consists of helium atoms. Each helium atom emitted will contribute to the decrease in atomic number by two, because atomic number of helium is 2.Hence radioactive decay leads to decrease in mass of the isotope.
:
: : Hi,
: : How the mass of an isotope like Ir-192 is reduced as the isotope decays?
------------ End Original Message ------------




 
01:16 Sep-28-2008

N.Kuppusamy

Consultant, NDT Level-III Engineer
Advanced Inspection & Testing (S) Pte Ltd,
Singapore,
Joined Dec 2003
34
Re: how mass is reduced as isotope decays? Mass and energy are equated with space and time.

Again mass and energy are related by E=mc2.

Where E = enegry, m = mass and c = velocity of light.

An atom reduces its mass by the emission of alpha, beta and other particle emissions.

When alpha particle is emitted the atomic number reduced by 2 and mass number reduced by 4.

Emission of beta particle result in increase of atomic number. The mass is governed by the nuclear forces of the daughter nucleus and binding energy.

Emission of positron result in decreased atomic number. Again the mass is governed by the nuclear forces of the daughter nucleus and binding energy.

When particles are emitted by atom the reduction of mass is significant, while mass reduction is not significant with the emission of electromagnetic radiation because even a tiny mass creates enormous energy according to Einstein's famous equation. Most of the cases emission of electromagnetic radiation (i.e. gamma) associated with particle radiation and ultimately all isotopes(heavy) end up their life when they transformed into Lead.

The electromagnetic radiation(gamma) is having a property called duality, i.e., it exists in particle as well as wave forms simultaneously.

When Energy is emitted the mass must be reduced. It is most fundamental to maintain law of conservation of energy which is the most fundamental of known physical laws. If mass is not reduced after the emission of energy (i.e., electromagnetic radiation), it violates the law of conservation energy.

How a particle acquired mass? - is the most fundamental question yet to be answered on which every body hope to get the answer from the CERN experiments.

Regards,

N.Kuppusamy

----------- Start Original Message -----------
: Dear Prabhu,
: That was a good explanation but alpha rays are Helium nuclei, not atoms. Atoms are electrically neutral and have electrons to neutralise the positive charge of the nucleus. Since most of the mass is accounted by the nucleus, the mass of the atom and the mass of the nucleus can be taken as same in many situations. Beta particles are electrons emitted by the nucleus and theoretically there is a small loss of mass but for all practical purposes, the same is ignored. Gamma rays are photons of electromagnetic radiation and have no mass.
: Regards.
: Swamy
: :
: : The decay of a radioactive isotope is nothing but emission of alpha, beta and gamma rays. Alpha rays consists of helium atoms. Each helium atom emitted will contribute to the decrease in atomic number by two, because atomic number of helium is 2.Hence radioactive decay leads to decrease in mass of the isotope.
: :
: : : Hi,
: : : How the mass of an isotope like Ir-192 is reduced as the isotope decays?
------------ End Original Message ------------




 
09:33 Sep-28-2008

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
515
Re: how mass is reduced as isotope decays? ----------- Start Original Message -----------
: Hi,
: How the mass of an isotope like Ir-192 is reduced as the isotope decays?
------------ End Original Message ------------

I fear that the various answer may have served to confuse further.

After the half life of an isotope the mass of that isotope present will have decayed to half of its original value.

However as an isotope decays it is converted into one or more new elements, having a total mass almost exactly the same. The only overall mass loss will be the weight of alpha particles (Helium nuclei, relatively heavy approx 4 AM units) beta particles (electrons, approx 0.0005 units) and the mass equivalent of emitted energy. In practice this is likely to be a negligible amount, of the order of parts per million or less, so no measurable overall mass loss will be observed .




 
06:50 Oct-06-2008

N.Kuppusamy

Consultant, NDT Level-III Engineer
Advanced Inspection & Testing (S) Pte Ltd,
Singapore,
Joined Dec 2003
34
Re: how mass is reduced as isotope decays? Hi,

There is a correction here. After one half-life the mass does not decayed to half of its original value. Only the activity is reduced by half.

The mass is reduced in different proportion depnding on the type of decay.

For example if an atom with mass no.8 emits alpha particle, it will reduce its mass by half after one half-life.

While Uranium 238 which is alpha emitter reduduced its mass by 4 units by changing into daughter nucleus of Th-234. That is, 238 gram of Uranium 238 (1mole) changed in to 119 gram of Uranium 238 (1/2 mole) and 115 gram of Thorium 234 (1/2 mole). The remaing mass after 1 half life is therfore 119+115=234 grams and 4 grams (1mole) of Helium emitted as alpha particles.

Regards,

nks

----------- Start Original Message -----------
: : Hi,
: : How the mass of an isotope like Ir-192 is reduced as the isotope decays?
: I fear that the various answer may have served to confuse further.
: After the half life of an isotope the mass of that isotope present will have decayed to half of its original value.
: However as an isotope decays it is converted into one or more new elements, having a total mass almost exactly the same. The only overall mass loss will be the weight of alpha particles (Helium nuclei, relatively heavy approx 4 AM units) beta particles (electrons, approx 0.0005 units) and the mass equivalent of emitted energy. In practice this is likely to be a negligible amount, of the order of parts per million or less, so no measurable overall mass loss will be observed .
------------ End Original Message ------------




 
07:20 Oct-06-2008

N.Kuppusamy

Consultant, NDT Level-III Engineer
Advanced Inspection & Testing (S) Pte Ltd,
Singapore,
Joined Dec 2003
34
Re: how mass is reduced as isotope decays? HI,

There is a mistake. Please correct it as follows:

There is a correction here. After one half-life the mass does not decayed to half of its original value. Only the activity is reduced by half.

The mass is reduced in different proportion depnding on the type of decay.

For example if an atom with mass no.8 emits alpha particle, it will reduce its mass by half after one half-life.

While Uranium 238 which is alpha emitter reduduced its mass by 4 units by changing into daughter nucleus of Th-234. That is, 238 gram of Uranium 238 (1mole) changed in to 119 gram of Uranium 238 (1/2 mole) and 117 gram of Thorium 234 (1/2 mole). The remaing mass after 1 half life is therfore 119+117=236 grams and 2 grams (1/2 mole) of Helium emitted as alpha particles.

1mole of U238 = 238 gram (initial) ; After 1 half life,

1/2 mole of U238 = 119 gram
1/2 mole of Th234 = 117 gram
1/2 mole of He4 = 2 gram
_____________________________
Total = 238 gram (after 1 half life)
_____________________________
Regards,

nks


----------- Start Original Message -----------
: Hi,
: There is a correction here. After one half-life the mass does not decayed to half of its original value. Only the activity is reduced by half.
: The mass is reduced in different proportion depnding on the type of decay.
: For example if an atom with mass no.8 emits alpha particle, it will reduce its mass by half after one half-life.
: While Uranium 238 which is alpha emitter reduduced its mass by 4 units by changing into daughter nucleus of Th-234. That is, 238 gram of Uranium 238 (1mole) changed in to 119 gram of Uranium 238 (1/2 mole) and 115 gram of Thorium 234 (1/2 mole). The remaing mass after 1 half life is therfore 119+115=234 grams and 4 grams (1mole) of Helium emitted as alpha particles.
: Regards,
: nks
: : : Hi,
: : : How the mass of an isotope like Ir-192 is reduced as the isotope decays?
: : I fear that the various answer may have served to confuse further.
: : After the half life of an isotope the mass of that isotope present will have decayed to half of its original value.
: : However as an isotope decays it is converted into one or more new elements, having a total mass almost exactly the same. The only overall mass loss will be the weight of alpha particles (Helium nuclei, relatively heavy approx 4 AM units) beta particles (electrons, approx 0.0005 units) and the mass equivalent of emitted energy. In practice this is likely to be a negligible amount, of the order of parts per million or less, so no measurable overall mass loss will be observed .
------------ End Original Message ------------




 


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