A nucleus made of protons and neutrons surrounded by a cloud of electrons equal in number to the protons.
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 ...
32
votes
3answers
1k views
Can the solar system really fit in a thimble?
Almost every time somebody talks about atoms, at some point they mention something like this:
If we remove the spaces between the atoms and atomic components, we can fit the solar system in a ...
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.
...
21
votes
6answers
2k views
Why does space expansion not expand matter?
REFORMULATED:
I have looked at the other questions (ie "why does space expansion affect matter") but can't find the answer I am looking for.
My question:
There is always mention of space expanding ...
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 ...
16
votes
7answers
2k views
Is mass quantized?
I learned today in class that photons and light are quantized. I also remember that electric charge is quantized as well. I was thinking about these implications, and I was wondering if mass was ...
14
votes
1answer
466 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
880 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, ...
9
votes
5answers
2k views
Which experiments prove atomic theory?
Which experiments prove atomic theory?
Sub-atomic theories:
atoms have: nuclei; electrons; protons; and neutrons.
That the number of electrons atoms have determines their relationship with other ...
9
votes
4answers
719 views
Why does amount of protons define how matter is?
My question might sound convoluted but my mind is twisting right now so my apologies in advanced.
Why is it that when I have one proton and one electron it is Hydrogen a clear flammable gas, and ...
8
votes
2answers
7k views
What is in the space between a nucleus of an atom and its electrons?
There is a common analogy about the structure of an atom, such as the nucleus is a fly in the centre of a sports stadium and the electrons are tiny tiny gnats circling the stadium (tip of the hat to ...
8
votes
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 ...
7
votes
2answers
278 views
why dosen't a charged particle radiate energy in circular motion in a uniform magnetic field?
I have studied in my Physics course that one of the drawbacks of Rutherford's atomic model was that when an electron will revolve around the nucleus, it is undergoing acceleration and so it should ...
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 ...
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 ...
6
votes
1answer
386 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 ...
6
votes
2answers
144 views
Do the energy levels of electron orbitals change relativistically?
When an electron emits a photon from changing energy levels, the frequency of the photon depends on the difference between the energy levels.
But if someone is moving with respect to the atom, the ...
5
votes
4answers
813 views
Atomic mass of Copper-63?
This URL lists the mass of Copper-63 as 62.9295975(6) and this other URL lists the mass as 62.939598. These values differ by almost exactly 0.01 which seems hard to explain by experimental error. ...
5
votes
2answers
789 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 ...
5
votes
4answers
661 views
Is there the smallest particle that can be guaranteed to be unable to be broken down into smaller particles?
Is there the smallest particle that can be guaranteed to be unable to be broken down into smaller particles?
5
votes
2answers
2k views
How does electron move around nucleus?
I need to get a nice picture about how electron moves around nucleus? I find concept of probability and orbitals quite difficult to understand?
5
votes
1answer
480 views
Open shells in Quantum mechanics of multielectron atoms
This question: How do electron configuration microstates map to term symbols?
And the discussion of multielectron effects here: Quantum Computing and Animal Navigation
Inspired me to try to understand ...
4
votes
3answers
1k views
Photon hitting an atom with higher energy than needed to ionize
Suppose we have an atom with several energy levels (e.g. an hydrogen), and it is hit by photons.
I know that in order to have the atom change energy levels, the photon must have an energy level ...
4
votes
2answers
135 views
Graphene +1 extra carbon bond
I'm not a physicist just a curious mind, so please go easy!
I was just watching a BBC Horizon Documentary that featured a piece on the recently discovered material Graphene. One of the facts ...
4
votes
4answers
232 views
Spontaneous radiation
The usual explanation of spontaneous radiation is that the energy eigenstates are perturbed by QED interaction, so that the eigenstates obtained from single-particle QM are no longer eigenstates of ...
4
votes
3answers
139 views
Do electrons in multi-electron atoms really have definite angular momenta?
Since the mutual repulsion term between electrons orbiting the same nucleus does not commute with either electron's angular momentum operator (but only with their sum), I'd assume that the electrons ...
4
votes
2answers
2k views
Zero probability of finding an electron in the nucleus
One and the same electron in a p orbital and taking part in a common π (pi) bond has two lobes visualized as connecting through the nucleus. There is however zero probability of finding an electron at ...
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.
...
4
votes
3answers
339 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 ...
4
votes
2answers
649 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 ...
4
votes
1answer
280 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 ...
3
votes
4answers
233 views
How can the nucleus of an atom be in an excited state?
An example of the nucleus of an atom being in an excited state is the Hoyle State, which was a theory devised by the Astronomer Fred Hoyle to help describe the vast quantities of carbon-12 present in ...
3
votes
4answers
958 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 ...
3
votes
4answers
548 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 ...
3
votes
2answers
242 views
Is it possible to recover the old Bohr-Sommerfeld model from the QM description of the atom by turning off some parameters?
Is it possible to recover the old Bohr-Sommerfeld model from the QM description of the atom by turning off some parameters?
Can we use Ehrenfest's theorem (or some other scheme) to reduce the QM ...
3
votes
2answers
120 views
Why is there a factor of 1/2 in the interaction energy of an induced dipole with the field that induces it?
In this paper, there's the following sentence:
...and the factor 1/2 takes into account that the dipole moment is an induced, not a permanent one.
Without any further explanation. I looked ...
3
votes
2answers
838 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 ...
3
votes
2answers
1k views
How does electron excitation relate to atomic orbitals?
Taking off from the Rutherford-Bohr model,
Figure 1. Rutherford-Bohr model.
when an electron absorbs energy (from light, heat, or otherwise) it jumps to a higher energy level, or shell. Then when ...
3
votes
3answers
180 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 ...
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 ...
3
votes
1answer
281 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 ...
2
votes
4answers
163 views
Computer Science Modeling of Physical World
I am curious what efforts have been made to date to define virtual computer worlds based on the physics we know in the real world?
I think it would be awesome to say start off with an atom defining ...
2
votes
2answers
281 views
Electrical neutrality of atoms
How is it that atoms with equal numbers of protons and electrons are described as "electrically neutral" when the proton is 1,800 times more massive than the electron?
2
votes
2answers
439 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 ...
2
votes
3answers
443 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 ...
2
votes
3answers
162 views
can I move the atom core only?
I was wondering if it is possible to move the atom core and leave behind the electrons. I can imagine that the electrons will follow the core. But what if the speed of the core is almost the same as ...
2
votes
2answers
390 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
3answers
4k views
Why is the relationship between atomic number and density not linear?
What are the factors that affect the density of an atom?
2
votes
1answer
64 views
How fast did hydrogen atoms travel when they were first formed in the early universe?
I can't seem to find any data on this, is it a known value?
2
votes
1answer
179 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 ...
