Nuclear physics is the study of the composition, behavior and interaction of atomic nuclei and their constituent parts.
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Why do electrons occupy the space around nuclei, and not collide with them?
We all learn in grade school that electrons are negatively-charged particles that inhabit the space around the nucleus of an atom, that protons are positively-charged and are embedded within the ...
12
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3answers
1k views
Protons' repulsion within a nucleus
Do the protons inside the nucleus repel each other by the electrostatic force? If they do, why doesn't the repulsion drive the protons apart so that the nuclei get disintegrated?
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5answers
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Conversion of mass to energy in chemical/nuclear reactions
Is mass converted into energy in exothermic chemical / nuclear reactions?
My (A Level) knowledge of chemistry suggests that this isn't the case. In a simple burning reaction, e.g. $C+O_2\to ...
7
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2answers
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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 ...
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1answer
184 views
What are the average matter, antimatter, and binding energy composition of protons and neutrons?
For a free baryon at rest at room temperature, how much of its ~1Gev (rest) mass can (on average) be considered as matter, as antimatter, and as binding energy?
For a baryon in a nucleus, I assume ...
32
votes
8answers
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What practical issues remain for the adoption of Thorium reactors?
From what I've read on thorium reactors, there's enormous benefit to them. Their fuel is abundant enough to power human civilization for centuries, their fission products are relatively short-lived, ...
10
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3answers
876 views
Age of the Earth and the star that preceded the Sun
One of the great unheralded advances made in the history of science was the ability to determine the age of Earth based on the decay of isotopic uranium. Based on the apparent abundance of uranium in ...
4
votes
2answers
185 views
What is an intuitive picture of the motion of nucleons?
I understand the "motion" of electrons within an ordinary atom (say argon at room temperature and pressure). They are moving in "orbits" defined by quantum mechanical wavefunctions where the "orbits" ...
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3answers
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Why don't electrons crash into the nuclei they “orbit”?
I'm having trouble understanding the simple "planetary" model of the atom that I'm being taught in my basic chemistry course.
In particular,
I can't see how a negatively charged electron can stay ...
7
votes
6answers
891 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 ...
6
votes
3answers
257 views
References on the non-compositeness of the known elementary particles
What paper(s) or theory(s) describe or prove that the elementary particles that we have determined today cannot be made up of smaller more fundamental particles?
6
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1answer
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Why doesn't orbital electron fall into the nucleus of Rb85, but falls into the nucleus of Rb83?
Rb83 is unstable and decays to Kr-83. Mode of the decay is electron capture. Rb85 is stable.
The nuclei Rb83 and Rb85 have the same charge. Rb85 is heavier than Rb85, but gravitation is too weak to ...
2
votes
2answers
466 views
What happens if we put together a proton and an antineutron?
A hydrogen nucleus consists of a single proton.
A 2-hydrogen (deuterium) nucleus consists of a proton and a neutron.
A tritium nucleus consists of a proton and two neutrons.
This makes me wonder how ...
14
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3answers
4k views
Why is the nucleus of an Iron atom so stable?
Lighter nuclei liberate energy when undergoing fusion, heavier nuclei when undergoing fission.
What is it about the nucleus of an Iron atom that makes it so stable?
Alternatively: Iron has the ...
4
votes
1answer
956 views
How to explain $E=mc^2$ mass defect in fission/fusion
What is the nature of nuclear energy? This is closely related to the correct explanation of mass defect.
I did some research of that topic and cannot come to a single comprehensive and consistent ...
9
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6answers
779 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 ...
11
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1answer
696 views
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 ...
8
votes
1answer
322 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 ...
4
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1answer
274 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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5answers
706 views
How does Positronium exist?
I've just recently heard of Positronium, an "element" with interesting properties formed by an electron and positron, and I was shocked to hear that physicists were actually working with this element, ...
8
votes
2answers
382 views
Are the protons and neutrons in the nucleus arranged in any particular way?
I was wondering this: suppose you have two oxygen atoms. They will both have 8 protons and 8 neutrons in the nucleus (at least if they are the most common isotope). Now, will all those particles be ...
7
votes
2answers
985 views
Having the same number of neutrons
Sorry if this is a silly question.
If I understand correctly, for two atoms "having the same number of protons" is equivalent to "being of the same element", while "having the same number of protons ...
5
votes
3answers
243 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 ...
5
votes
2answers
702 views
Tunneling of alpha particles
Consider this explanation of the alpha decay: It says
The Coulomb barrier faced by an alpha
particle with this energy is about 26
MeV, so by classical physics it cannot
escape at all. ...
4
votes
2answers
660 views
Origin of elements heavier than Iron (Fe)
In all the discussions about how the heavy elements in the universe are forged in the guts of stars and especially during a stars death, I usually hear that once the star begins fusing lighter atoms ...
3
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1answer
191 views
Is it possible that nuclear fission contributes to climate change?
This is probably a really stupid question, please forgive me.
Is it possible that the use of nuclear fission on earth contributes to the increased energy in the Earth's system as according with the ...
3
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2answers
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Strongest force in nature
Possible Duplicate:
What does it mean to say “Gravity is the weakest of the forces”?
It is said nuclear force is the strongest force in nature..
But it is not true near a black ...
2
votes
4answers
2k views
Where do electrons get their ever-lasting circulating energy?
We all know (or maybe know) that to move, we need to spend energy. If you want to drive a car, you gotta spend gasoline.
We also know that energy can't be created (first law of thermodynamics, and ...
6
votes
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) ...
14
votes
1answer
467 views
Turned to steel in the great magnetic field
This is obviously a "fun" question, but I'm sure it still has valid physics in it, so bear with me.
How great of a magnetic field would you need to transmute other elements into iron/nickel, if ...
10
votes
3answers
764 views
Why some nuclei with “magic” numbers of neutrons have a half-life less than their neighbor isotopes?
It's easy to find the "magic" numbers of neutrons on the diagrams of alpha-decay energy: 82, 126, 152, 162. Such "magic" nuclei should be more stable than their neighbors.
But why some nuclei ...
11
votes
5answers
736 views
How many times has the “stuff” in our solar system been recycled from previous stars?
Is there a cosmologist in the house? I've got a basic understanding (with some degree of error) of some simple facts:
The Universe is a little over 13 billion years old. Our galaxy is almost that ...
4
votes
0answers
347 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 ...
2
votes
1answer
417 views
How much energy can be extracted from hydrogen?
http://en.wikipedia.org/wiki/B-L says that the difference between baryon number and lepton number is conserved. Ordinary hydrogen has one of each, but turning it into helium releases only the binding ...
10
votes
4answers
385 views
How do we know that the nucleus isn't a quark-gluon plasma?
The standard picture of the nucleus of atom is that is several distinct nucleons, which themselves are composed of quarks. However, it seems to me like a much simpler picture is that the nucleus is ...
8
votes
4answers
176 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 ...
6
votes
2answers
144 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 ...
4
votes
2answers
121 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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vote
3answers
351 views
Please explain C14 half-life
I understand that C14 decays at a given rate. I also interpret this to mean that 100% of the atoms of C14 in an object will all decay at the same right, individually.
So if I have 4 C14 atoms, will ...
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votes
1answer
106 views
Direct nuclear reactions problems [closed]
can anyone explain Multi-step nuclear reactions in terms of direct nuclear reactions .
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4answers
218 views
Which part of making an atomic bomb is the hard part and how many people know how to do that? [closed]
I mean which part of the process of making an Atomic bomb is the hard and how many people know how to do that on Earth. Is it in hundreds or less i.e. 20 - 50 people or even less?
Don't get me wrong ...
8
votes
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?
5
votes
3answers
215 views
We're all star dust?
OK so we've all heard of this from Carl Sagan, Lawrence Krauss and others and we know the argumentation, I don't refute that. There are other examples, for instance I once calculated (this was before ...
5
votes
3answers
280 views
Do neutron stars reflect light?
The setup is very simple: you have a regular ($1.35$ to $2$ solar masses) evolved neutron star, and you shine plane electromagnetic waves on it with given $\lambda$. Very roughly, what shall be the ...
4
votes
0answers
58 views
Can we excite a nucleus by means of very intense low energy gamma-photon irradiation?
The phenomenon of multiphoton ionisation of atoms has been studied, both theoretically and experimentally, for several decades. Intense LASER beam devices are the apparatuses used for the experimental ...
3
votes
1answer
58 views
The synthesis of $^{254}\text{No}$
How is $^{254}\text{No}$ synthesised?
Could you explain the reaction where it is preceded by $^{208}\text{Pb}(^{48}\text{Ca}, 2\text{n})$?
References to articles are well enough—I was somehow unable ...
3
votes
2answers
162 views
Is there an equation for the residual strong nuclear force?
First of all, note the qualifier "residual". The present question is not the same as that asked, and answered, in the StackExchange question "Is there an equation for the strong nuclear force?" which ...
3
votes
1answer
340 views
gamma ray lasers?
Is it really possible in the foreseeable future to create a gamma ray laser? I've read these two articles on Wikipedia:
the Hafnium controversy
Induced gamma emission
It sounds pretty amazing, ...
3
votes
2answers
142 views
Pressures Necessary for Carbon Detonation
Carbon detonation is a characteristic event of Type 1a Supernova (EDIT: where an accreting white dwarf near the Chandrashankar limit of 1.4 solar masses explodes), an extremely important standard ...
2
votes
1answer
777 views
Does the Breit Wigner formula apply to intermediate virtual particles?
Breit Wigner Formula describes the cross section for interactions that proceed dominantly via a intermediate particle (O*) A+B → O* → C + D:
$$σ = \frac{2\Pi}{k^{2}}\frac{Γ_{i}Γ_{f}}{(E-E_{o})^{2} + ...
