The property of some materials by which individual atoms decay, emitting energy or particles often transforming into different elements in the process.
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Why is technetium unstable?
Is there a simple account of why technetium is unstable?
From the Isotopes section of Wikipedia's article on Technetium:
Technetium, with atomic number (denoted Z) 43, is the lowest-numbered ...
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6answers
1k views
Since radioactive material decays how is it possible that there is any left after 4.5 billion years?
I was not able to find an answer for this question...
Some radioactive elements have half-life measured in thousands of years and some others even in millions, but over 4.5 billion years all the ...
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6answers
778 views
Is there any thing other than time that “triggers” a radioactive atom to decay?
Say you have a vial of tritium and monitor their atomic decay with a geiger counter. How does an atom "know" when it's time to decay? It seems odd that all the tritium atoms are identical except with ...
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2answers
1k views
Why are alpha particles made of 2 protons and neutrons?
When experiencing alpha decay, atoms shed alpha particles made of 2 protons and 2 neutrons. Why can't we have other types of particles made of more or less protons?
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1answer
343 views
Why is carbon dating limit only 40,000 years?
For an example, when they tried to get the carbon dating for presence of Aboriginal people in Australia they get to the number 40,000. But it could be much earlier. Why is that 40,000 years limit for ...
8
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4answers
173 views
Why are alpha particles such a prominent form of radiation and not other types of nucleon arrangement?
It is said in many textbooks that alpha decay involves emitting alpha particles, which are very stable. Indeed, the binding energy (~28.3 MeV) is higher than for $Z$-neighboring stable isotopes. But ...
8
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1answer
320 views
Island of Stability
When I was much younger, I remember being fascinated by the thought of an Island of Stability at very high atomic numbers. However, I have not heard much on this and I was wondering
Did this idea ...
8
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2answers
78 views
Radio-dating and the age of the earth
I understand there are a few radio-dating methods to determine the age of the earth, uranium-lead to name one (maybe not the best though). The ratio Pb206 + Pb207 to U allows you to find when the ...
8
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4answers
409 views
strange modulation of radiactive decay rates with solar activity
Recently i found out this uber strange article about nuclear decay rates being somehow showing seasonal variations with a high correlation with sun activity. Two very precise questions:
1) has this ...
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6answers
885 views
How do we know that C14 decay is exponential and not linear?
In my previous question I asked Please explain C14 half-life The OP mentioned that I was thinking of linear decay and C14 was measured in exponential decay.
As I understand it, C14 is always in a ...
7
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2answers
1k views
How do we know that some radioactive materials have a half life of millions or even billions of years?
If a radioactive material takes a very long time to decay, how is its half life measured or calculated? Do we have to actually observe the radioactive material for a very long time to extrapolate its ...
7
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2answers
500 views
Mars Curiosity Power System
Curiosity's power source comes from a radioisotope thermoelectric generator (RTG) rather than from solar panels like the two Mars Rovers. 2,000 watts of thermal power from alpha particle emission in ...
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4answers
582 views
Can you speed up radioactive decay of plutonium?
We all know the issue of deep geological repositories for fuel rods. Is there a way to speed up the rod's decay to render them harmless in less than 10 years?
6
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1answer
164 views
Radioactive nuclear fuel?
I suppose this is a not-too-bright question but, in a nutshell: why are nuclear fuels radioactive?
With this I mean, which is the connection between being a fissile (or fertile, for that matter) ...
6
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2answers
140 views
Radioactive Decay
Problem:Nuclei of a radioactive element $\Bbb X$ having decay constant $\lambda$ , ( decays into another stable nuclei $\Bbb Y$ ) is being produced by some external process at a constant rate ...
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5answers
296 views
Radioactive decay, why such unintuitive formula?
When talking of exponential decay, as with radioactive decay, the formula used (e.g. Wikipedia and my textbook) is:
$$
N(t) = N_0e^{-\lambda t}
$$
This formula, with the decay constant $\lambda$ ...
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3answers
409 views
Can electricity transfer radioactivity?
If a cable used to power something is exposed to a radioactive source will it over time make the entire cable radioactive?
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3answers
238 views
Do some half-lives change over time?
I was recently doing some physics tuition on radioactivity and the student claimed her chemistry teacher had said that radioactive substances can be grouped into two divisions: those whose half-life ...
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3answers
317 views
What is happening over the 15 minutes it takes a neutron to decay?
I've read that free neutrons decay into a proton, electron and neutrino with an average lifespan of about 15 minutes. Is there anything physically different about a neutron that has existed for 14 ...
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3answers
239 views
Is there a way to decrease the rate of nuclear Beta decay?
In that question and its answers it was mentioned that you could trigger radioactive decay by bombarding atoms with gamma rays of the right energy level (there may be other solutions I do not know ...
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2answers
509 views
What other shielding material than lead is effective against gamma rays?
As the question in the title states I am wondering what material can be effectively used to shield gamma rays apart from lead? I believe concrete is often used, but it is nowhere near as effective as ...
5
votes
1answer
409 views
What happens to chemical compunds that include radioactive nuclei, when those decay?
Say you have a chemical compound made up of one or more radioactive nuclei. If the nucleus decays, does the compound?
Possible outcomes I can think of:
the compounds continues to exist if a ...
4
votes
2answers
166 views
Is there a direct relationship between an isotope's neutron count and radioactivity?
In my textbook, it lists isotopes of Carbon: C-12, C-13, and C-14. It noted that C-14 is radioactive (C-12 and C-13 are not).
Is there a direct relationship between the number of neutrons and an ...
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2answers
864 views
Why is beta negative decay more common than beta positive?
In simple terms, why is beta negative decay more common than beta positive?
I know it's something to do with occuring inside/outside the nucleus - but I can't find a simple, easy to understand ...
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1answer
205 views
can radiocarbon dating be used on living things?
I have been going through a wiki article about worlds oldest living creature. As a matter of fact its a plant, a shrub to be precise.
Wiki says that the plant age was determined by carbon dating. But ...
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votes
5answers
339 views
What needs to happen for one to ingest radioactive particles and how likely is this?
There are many stories about radioactivity and the relative danger of it in the news lately, but very little actual information. The radioactivity levels around Fukushima Daiichi are high, but seem ...
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2answers
120 views
nuclear fission and half life
Why is the alpha, beta or gamma decay of an unstable nucleus unaffected by the chemical situation of an atom, such as the nature of the molecule or solid in which it is bound? The chemical situation ...
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2answers
404 views
Predicting Decay Rates via the Standard Model
Question 7584 illustrated a procedure to forecast the decay rates of isotopes with known long average lifetimes. Lifetimes of the many U isotopes vary from micoseconds to gigayears. F has only one ...
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1answer
270 views
Why are synthetic elements unstable?
So far 20 synthetic elements have been synthesized. All are unstable, decaying with half-lives between years and milliseconds.
Why is that?
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3answers
133 views
How do we know that internal conversion creates no intermediate photon?
I've read, from several sources, that in internal conversion -- an excited electron transferring its energy to another electron which is then emitted -- no intermediate gamma radiation is produced.
...
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1answer
824 views
Gravity and Planetary Differentiation
During solar system formation, many bodies achieved hydrostatic equilibrium, a spherical shape where their self gravitational force was balanced by internal pressure. Many also achieved ...
4
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1answer
289 views
Dangerous dose of I-131?
I was searching a lot and could only find dosages for curing cancer and allowed emission, but no Iodine-131 dose that could be connected with increased thyroid cancer risk (like, 10mSv is the ...
4
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0answers
344 views
Long time deviations from exponential decay in radioactivity
Are there any examples of common substances whose decay is not exponential?
We're used to thinking about radioactivity in terms of half-lives. This is a concept that makes sense only for a decay that ...
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votes
4answers
879 views
Alpha Beta Gamma Biological Impact
Assume that alpha & beta particles and gamma photons each reach skin at the same energy. It's known that they penetrate most deeply in order by gamma, beta and alpha. How would they compare in ...
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2answers
546 views
Effect of temperature on radioactivity?
I'm researching the effect of temperature on uranium radioactivity, however I can't find any solid empirical evidence to prove the notion that temperature does not affect radioactivity.
Can anyone ...
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2answers
181 views
Can one see radioactive substances with an X-ray detector?
I was wondering the other day an X-ray detector (like the ones used at airports) can detect gamma-rays lets say from a sample of uranium. I know its all electro-magnetic waves but I'm really unsure ...
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1answer
217 views
The vacuum as trigger
Do the apperance in the atomic nucleus of virtual matter-antimatter particle pairs play a role in the random nature of radioactive decay?
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6answers
4k views
Why do they consider radioactive matter with long half lives more dangerous than matter with a short half life?
The title says it all.
For example why is plutonium considered more dangerous than radioactive iodine?
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5answers
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Iodine-131 half-life and reality
Iodine is a chemical element with symbol I and atomic number 53.
There is currently a lot of discussions regarding radioactivity in Japan, and iodine-131.
Iodine-131 has a half-life of 9 days.
Does ...
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4answers
264 views
Changing the Half-Life of Radioactive Substances
Is there a way to extend or reduce the half-life of a radioactive object? Perhaps by subjecting it to more radiation or some other method.
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5answers
221 views
Thorium radioactivty vs Uranium radioactivty nuclear power
May i please open this question by asking that if you intended to answer this please could you provide links based on your answer. I have read ( and posted one ) on thorium and a lot of the answers ...
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1answer
76 views
Radioactivity and quantum superpositions
In the Schrödinger's cat experiment 'there is a tiny bit of radioactive substance, so small that perhaps in the course of the hour, one of the atoms decays'. The rest of the experiment magnifies this ...
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1answer
48 views
XP Decay mode of radioactive nucleus
The decay mode of Carbon-8 is listed as 'XP' in this table. None of the references I looked at listed XP as a decay mode. What is it>
2
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1answer
121 views
How was Be-8's Half-Life of 7E-17 Second Determined?
Radionuclides occur with half-lives in a vast range of over 37 magnitudes as listed in this site. In question 7584, Lubos Motl explained how Gyr half-lives were determined. This method doesn't appear ...
2
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1answer
154 views
Can stable nuclei theoretically fission through quantum tunneling?
As I understand it, an unstable nucleus is going to randomly fission because the forces binding it together are momentarily weaker than the electrostatic repulsion of the protons.
Given that some ...
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1answer
83 views
Creation of Nuclear Isomers
As I understand it, if a nucleus is excited with energy exceeding its ground state, it releases energy via gamma radiation. An example would be technitium 99m, a medical tracer with a 6 hour half life ...
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3answers
854 views
Work of Marie Curie?
I've been reading about the work of Marie Curie recently after a friend filled me in on what she did (never having had much of an idea previously) and it's all very interesting.
What I can't ...
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2answers
447 views
Iodine isotope question
Quick question for the nuclear engineers/physicists out there
Where does I-134 come from? I cant find it in any of the charts of standard decay products of Uranium fission, but there is tons of the ...
2
votes
1answer
83 views
Program for radiation and toxic hazards
I worked in my masters thesis with $^{87}Rb$ and $^{40}K$, really small beta emitters. But there are so many other things around in the lab, that I want to keep track on all the things I might get in ...
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2answers
903 views
How to calculate gamma radiation shielding?
A device emits 0.2 μSv/h of gamma rays. How thick does an aluminum sheet need to be to completely stop radiation from coming out ? What equation is to be used to calculate this ?
