A nucleus made of protons and neutrons surrounded by a cloud of electrons equal in number to the protons.
3
votes
4answers
976 views
Bohr's model of an atom doesn't seem to have overcome the drawback of Rutherford's model
We, as high school students have been taught that-because Bohr's model of an atom assigns specific orbits for electrons-that it is better than Rutherford's model. But what Rutherford failed to explain ...
1
vote
3answers
91 views
How can a strong water current be cold
This is a layman question.
If heat is the motion of atoms, how can a fast moving water current be cold?
1
vote
2answers
236 views
A basic confusion about what is an atom
Wikipedia defines atom as
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons.
and defines electron as:
The ...
1
vote
0answers
24 views
How the radio-freqency magnetic field helps to record fluorescence signal
Suppose a sample of atoms (say rubidium), which is exposed to constant magnetic field, is irradiated with circularly polarized light so that the electrons are excited from lower S level (F=3) to P ...
6
votes
3answers
261 views
Is hydrogen the same everywhere?
Silly thought. Feel free to shoot it down
Does a hydrogen atom undergo any kind of change subject to it's environment?
If one were to study a hydrogen atom on the surface of Mercury, another above ...
1
vote
1answer
446 views
Doping of pentavalent atom with hexavalent atom
We know that a tetra valent element can be a semiconductor and doping of pentavalent and trivalent impurities would give a extrinsic semiconductor.
I got a question now. Can we use an element of ...
2
votes
2answers
394 views
Is there a list of all atomic electron state transitions and the corresponding radiation emitted?
Here's a quote from Wikipedia:
As an example, the ground state configuration of the sodium atom is 1s22s22p63s, as deduced from the Aufbau principle (see below). The first excited state is ...
2
votes
0answers
98 views
Does this photon emission problem even make sense?
I came across this question in an introductory physics course awhile back and I never got over it: "A hydrogen atom has an electron in the n=5 orbit, what is the maximum number of photons that might ...
1
vote
1answer
64 views
Complex Atom Manipulation?
Is it theoretically possible for humans to manipulate Atoms to the extent that we can recreate anything we want?
e.g.
'Computer, Milky Way Bar please [or other].' (out pops a Milky Way Bar after some ...
0
votes
1answer
1k views
Anomalous Expansion Of Water
How can the Anomalous Expansion of Water from 4$^\circ$C to 0$^\circ$C be explained with reference to subatomic particles?
0
votes
1answer
338 views
The Nucleus of an Atom
We know that the protons in a nucleus are positively charged, whereas the neutrons do not possess a charge; we also know that unlike charges attract. So why does the nucleus stay intact, even though ...
0
votes
1answer
67 views
My book uses helium weight in reaction formula instead of weight alpha particle?
I'm suppose to write out reactions where atoms send out alpha radiation and decay. The book uses the 4-2 H, 4 as nucleon number and 2 as proton number, but isn't that wrong? The mass of helium is ...
2
votes
1answer
136 views
Atomic weight in respect to the binding energy?
My book says that the weight of helium (with the nucleon number of 4 and proton of 2) is that of $6,6447*10^{-27}$ kg. Earlier the book stated that if the proton number is left out it means that the ...
3
votes
2answers
842 views
Bohr Model of the Hydrogen Atom - Energy Levels of the Hydrogen Atom
Why the allowed (stationary) orbits correspond to those for which the orbital angular momentum of the electron is an integer multiple of $\hbar=\frac {h}{2\pi}$?
$$L=n\hbar$$
Bohr Quantization rule of ...
0
votes
2answers
201 views
How can particles being closed strings in String Theory create solidity in objects?
I understand how particles with certain masses can form to make atoms, which create solidity in objects due to Pauli's Exclusion Principle and what have you. These particles actually have mass and to ...
41
votes
6answers
4k views
What does it mean for two objects to “touch”?
If you've ever been annoyingly poked by a geek, you might be familiar with the semi-nerdy obnoxious response of
"I'm not actually touching you! The electrons in the atoms of my
skin are just ...
4
votes
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.
...
2
votes
4answers
659 views
How can one describe electron motion around hydrogen atom?
I remember from introductory Quantum Mechanics, that hydrogen atom is one of those systems that we can solve without too much ( embarrassing ) approximations.
After a number of postulates, QM ...
2
votes
1answer
242 views
Implementing simple atom model using density functional theory (DFT)
I am trying to write computer code which will find the energy and density function for a atom with Z protons and N electrons. I am working in 1D for simplicity and would like to make the overall code ...
2
votes
2answers
257 views
Why does optical pumping of Rubidium require presence of magnetic field?
The optical pumping experiment of Rubidium requires the presence of magnetic field, but I don't understand why.
The basic principle of pumping is that the selection rule forbids transition from ...
2
votes
2answers
253 views
At what angle does a single atom “reflect” a single photon?
Does this question make sense in the quantum world?
Imagining a single photon (wave packet?) interacting with a single atom (its electrons etc) how do we currently describe/define the emitted photon ...
3
votes
2answers
318 views
Is the electron wave function defined during photon emission
I have heard the term quantum leap to describe the (instantaneous?) transition from a higher energy orbital to a lower energy orbital. Yet, I understand that this transition time has now been ...
0
votes
0answers
312 views
Evaluating Transition probability between different states of Hydrogen atom
I am trying to evaluate the inner product $<2S_{\frac{1}{2}},F',F'_{3}|\delta^{3}(x)\sigma_{i}P_{i}|2P_{\frac{1}{2}},F,F_{3}>$ It's written in the form $<nl_{j},F,F_{3}|$ Where ...
1
vote
1answer
117 views
Working with atomic (?) units in solid state physics
I'm having some troubles understanding the units used in solid state physics paper. In the paper I read
$\Lambda a \sim 1$
where $\Lambda$ is a momentum cutoff and $a$ is the lattice spacing of a ...
1
vote
1answer
86 views
Peaks on top of Bremsstrahlung
The following is a graph of the intensity of Bremsstrahlung generated by accelerating electrons to hit a target vs. its wavelength.
I'm wondering what causes the additional peaks for high energies? ...
21
votes
3answers
1k views
Why do we need 12 atoms to store 1 bit of data?
Recent research at IBM has found a way to store 1 bit of data in 12 atoms.
While that is a big accomplishment compared to what we have today, it does seem like a waste to a non-physics eye like me.
...
18
votes
3answers
3k views
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 ...
2
votes
1answer
502 views
Nanotech - zero dimensional fullerene
Not really a physics junkie, and I think this is a chemistry question, but since there's no chemistry.stackexchange.com (yet) I think here is the best place.
I was just reading up on nanotech and ...
2
votes
2answers
472 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 ...
1
vote
3answers
202 views
Is energy conserved in decay of hydrogen atom in superposed state?
This looks like a paradox.
Let's say we have an hydrogen atom. Superposition of states could be possible for electrons. But if an electron is in a superposition, I guess it could decay into a lower ...
1
vote
3answers
176 views
Atom Theory vs Quantum Physics
This never really occurred to me until now, so maybe it does not categorize a really important question, but according to Quantum theory anything that "is not observed is probability until it is ...
0
votes
0answers
79 views
What keeps an electron from flying into the nucleus of an atom? [duplicate]
Possible Duplicate:
Why do electrons occupy the space around nuclei, and not collide with them?
My understanding is that electrons are attracted to protons, and vice-versa.
Why don't the ...
4
votes
3answers
342 views
Planetary model of atom still valid?
When I was in school, I learned (from Democritus) that an atom was
similar to a solar system, with the nucleus being the sun, and the
electrons being the planets. Of course, there are some ...
5
votes
2answers
791 views
Is the Mendeleev table explained in quantum mechanics?
Does anybody know if there exists a mathematical explanation of Mendeleev table in quantum mechanics? In some textbooks (for example in "F.A.Berezin, M.A.Shubin. The Schrödinger Equation") the authors ...
4
votes
2answers
662 views
Is a given volume of sparkling water lighter or heavier than the same volume of still water?
I can see it two ways - if all the $CO_2$ has turned into bubbles I would imagine it is lighter. However dissolved $CO_2$ atoms are probably heaver than the $H_2O$ atoms they replace, or fit in ...
2
votes
1answer
182 views
Small confusion related to leaving of electrons from atoms
Picking up a circuit board from a table, or our clothing rubbing as we walk, sit and work, are all examples of movement that can create static charge. One object, or surface, picks up additional ...
0
votes
2answers
127 views
Synthesizing elements (Nuclear Physics/Alchemy?)
Based on my limited knowledge of nuclear physics, it seems that one day it may/will be possible to synthesize whatever elements we may need, given enough energy. Is this accurate?
Is there a table ...
3
votes
3answers
181 views
Do we have control on what an electron transition emits: light or heat?
I don't know quantum mechanical model. So, I'm referring to just bohr's model of atom.
Any atom emits energy when it makes transition from higher excited state to lower excited state. Now, some times ...
1
vote
2answers
191 views
Subshell notation for hydrogen cation?
Looking at $s$,$p$,$d$ configuration for atoms & ions: Since a hydrogen cation $H^+$ has no electron, how would the subshell notation be written? My best estimate would be $1s^0$.
3
votes
4answers
564 views
is an electron/proton gun possible?
In the 1944 SF story "Off the Beam" by George O. Smith, an electron gun is constructed along the length of a spaceship. In order to avoid being constrained by a net charge imbalance, it is built to ...
-1
votes
1answer
627 views
Radial Schrödinger equation
I found a problem that says:
Show by direct substitution that $R_{10}$ is a solution of Schrödinger's radial equation.
AFAIK Schrödinger's radial equation is
...
2
votes
1answer
123 views
How much lead is there in the universe?
I know there is around 10^80 atoms in the observable universe, but is there any estimate the amount of lead in the universe (within a couple magnitudes of 10)?
3
votes
1answer
283 views
What are independent parameters in Hellmann–Feynman theorem?
A typical example in textbooks about the application of Hellmann–Feynman theorem is calculating $\left\langle\frac{1}{r^2}\right\rangle$ in hydrogen-like atoms. Wikipedia has a nice demonstration of ...
1
vote
2answers
2k views
Comparing scales of atomic level objects to scales of everyday size objects
I am trying to come up with everyday size objects comparisions of atomic scales items, e.g. if a proton probability cloud was of size basketball how far would the next atoms to it be?
reason being is ...
6
votes
1answer
248 views
Why atomic bomb makes a mushroom?
Atomic bombs make mushroom. It's well-known and we've seen many images of atomic experiments around the world. My question is, why mushroom? Does TNT and Grenade also make mini-mushrooms? Is it a ...
10
votes
3answers
886 views
What really cause light/photons to appear slower in media?
I know that if we solve the maxwell equation, we will end up with the phase velocity of light is related to the permeablity and the permitivity of the material. But this is not what I'm interested in, ...
2
votes
3answers
447 views
If an atom is fully ionized by removing all electrons, is it still an atom?
This is a question about terminology. To me, it's clear that the nucleus of an atom is still an atom. But a comment by Willie Wong at Is nature symmetric between particles and antiparticles? raises ...
4
votes
1answer
287 views
Why can free lithium atoms not take part in an Auger process?
Shouldn't it be possible for an incoming photon to excite one of the 1s electrons to a 2p state (or one of even higher energy) and then for the excited electron to drop back to 1s and kick out the 2s ...
1
vote
2answers
237 views
Photon emission from excited atoms
the answer given by classical quantum mechanic to the for atomica levels does not provide that an electron in an excited levels can radiate a photon and move to a lower level. How QED justifies this ...
6
votes
1answer
392 views
Is Palladium an exception?
I have been taught in school that atoms cannot have more than 8 electrons in the outer shell. Palladium atom's electron configuration is 2,8,18,18. Why isn't it 2,8,18,17,1 like the case of Platinum ...
