Questions tagged [atoms]
A nucleus made of protons and neutrons surrounded by a cloud of electrons equal in number to the protons.
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0answers
41 views
The energy mass equivalence relation [on hold]
I wanted to know that what is the reason we believe that the energy mass equivalence relation i.e. E = mc^2 is true?
What experiments other than that on the nucleons, compels us to believe this is ...
2
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1answer
81 views
Why atomic masses are quoted with reference to an isotope?
Is there any fundamental reason why atomic masses are quoted with respect to a certain element such as an arbitrary C-12 isotope whose mass has been set to 12 unit exactly? Previously, chemists have ...
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0answers
24 views
Is synchronized radiation possible?
Could it be possible to make 2 or more radioactive atoms, maybe plutonium, emit radiation at the same time? A kind of synchronized radiation. Perhaps this can be the basis for some kind of laser too.
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2answers
26 views
Rabi flopping vs. rate equation approach?
In Chapter 7 of C. J. Foot's Atomic Physics, Foot discusses the interaction of a two-level atom with radiation. He derives the phenomenon of Rabi flopping from the Schrodinger equation, using ...
0
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0answers
9 views
Why does Magnesium burn hotter than other Group 2 elements?
It seems apparent, when one performs the standard "flame tests" in a lab, for the Group II elements that Magnesium burns by far the hottest and brightest. Why is this true?
I wouldn't expect this at ...
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0answers
29 views
What is the upper limit for the size of an atom? [duplicate]
I read an article saying an Israeli scientist had discovered the heaviest nucleus with 122 protons and 170 neutrons, and found it in a sample of purified thorium, and I would like to know if there are ...
0
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1answer
80 views
How much distance is there between electrons in an electron shell? [closed]
I imagine they would need keep a certain distance away from each other.
2
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1answer
53 views
What is the principal cause of diffraction?
I have found another question similar to mine here. But I want to know why does diffraction of light happen in the first place. I have found other resources on google which explain the topic partially ...
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0answers
18 views
Expectation value of coordinate mixed operator with ground state
I have a Hamiltonian of the Hydrogen atom:
$H=H_0+H_1+H_2$ , when: $H_0 $ is the hamiltonian from central force and from electron momentum , $H_1$ is the relativistic kinetic fixing, and $H_2$ is the ...
1
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2answers
50 views
Can we use a camera with a frame rate of 1 trillion FPS to observe electrons, protons, and neutrons?
Like with this camera from MIT that works at 1 trillion FPS: https://youtu.be/EtsXgODHMWk
2
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2answers
34 views
Energy change during electron transitions
I was studying Bohr's atomic model and came to know that when electrons make transitions in between the orbits they lose or gain energy in the form of electromagnetic radiations. I understand why they ...
0
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3answers
48 views
formation of atomic nuclei from nucleons
What holds the nucleus together? In a nucleus there are several
protons, all of which are positive. Why don't they push themselves
apart? It turns out that in nuclei there are, in addition to
...
1
vote
1answer
67 views
Where does the momentum go when atom absorb a photon? [duplicate]
Imagine an electron around an atom absorbs a photon and becomes excited, it has now jumped to a higher orbital. At this point in time, where does the momentum of the photon goes?
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1answer
91 views
Whether this proof regarding Bohr's second postulate is true or false?
Let us assume a particle oscillating with displacement $x$.
Now $x = A\sin(2πft)$
$$\frac{\mathrm d x}{\mathrm dt} = v = 2πfA\cos(2πft)$$
Now $KE_\text{max}$ can be given when cosine value is 1; ...
1
vote
2answers
25 views
Variation of electronic energy levels $E_{nl}$ of a many-electron with $n$ and $l$
Within the central field approximation, the electronic energy levels $E_{nl}$ depend on both $n$ and $l$.
For a given value of $n$, $E_{nl}$ increases with increasing value of
$l$.
For a given ...
15
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7answers
4k views
How does Brownian motion prove the existence of atoms?
I have heard many people say that the existence of atoms is proven by Brownian motion. Now, I understand how an atomic theory would suggest the existence of Brownian motion. However, who is to say ...
0
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0answers
39 views
How can Coulomb's Law work in derivation of atomic radius? [duplicate]
Coulomb's Law for the force between two charges do not work for moving charges. For a single electronic atom, the electron moves around the nucleus. But in deriving the formula for finding an atom's ...
1
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2answers
46 views
Rutherford gold experiment
When an alpha particle is nearing the gold atoms nucleus, it is slowing down due to electrostatic repulsion, right?
But then why is the acceleration or velocity not a minimum at that point (the ...
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2answers
36 views
What is the relation between difraction and energy levels?
Imagine I have an atom in the cold space. The energy gap between its current energy and the next is exactly equals to the photons energy that is about to meet an atom. Atom absorbs photon. All is fine,...
1
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2answers
81 views
Entanglement in atoms, nuclei and quantized fields
Are the particles that are bounded by chemical bonds or nuclei joined by nuclear forces entangled or are they pure states?
In addition to that, are the subatomic particles in the atoms and nuclei, ...
1
vote
2answers
64 views
Can we show that the ground state of the He atom is a spin singlet rather than triplet?
The ground state of Helium atom is a state in which the space part of the wavefunction is symmetric and the spin part is antisymmetric under the exchange of the electrons. Therefore, the ground state ...
1
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0answers
22 views
How to estimate the mobility of atoms implanted in the interstitials and/or vacancies of a crystal?
I would like to compare the likelihood for implanted helium atoms to move from interstitials/vacancies of a crystal versus neon atoms. I read in the literature that He atoms located in interstitials/...
1
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2answers
69 views
How can high voltage create ions?
So I was reading about Tesla Coil propulsion and Ion Thrusters.
The thing I don't understand is the following:
As it is shown on the image, when an electron colides into a gas atom, it ionizes it. ...
4
votes
4answers
207 views
How do orbitals exist in an atom?
I have come across a picture online which talks about 1s,2s,2p orbitals of a sodium atom.
Observation:In the picture we see some volume of space in common to two orbitals.
For example:The circled(...
0
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2answers
53 views
Electron movement in 3d Bohr model
During a thought experiment, I observed that I was not able to figure the Bohr model in 3d.
In every picture I saw up to today, the electrons orbit the nucleus on a fixed circle-like path.
But while ...
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2answers
75 views
Is there a link between nuclear radiation and sound? [closed]
I'd like to understand if it's possible to relate/imagine a link or relationship between nuclear radiation and sound. A simple description would be appreciated since I don't have a deep understanding ...
1
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1answer
65 views
How can an ion ever capture an electron if an electron requires a precise momentum to match a subsequent orbital?
Suppose an electron approaches a proton with greater energy than the hydrogen ground state. Will the electron scatter? If so, how could an electron ever be captured given it would require exactly the ...
1
vote
1answer
66 views
If you were to be crossed by a wire the width of a single atom, would you still be split in half? [duplicate]
Supposing it is solid and wouldn't snap or break. Would it guillotine you or just pass through leaving you unwounded?
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1answer
58 views
Why ferromagnetism requires exactly 2 electrons in the last orbit?
All magnetic materials like iron, cobalt etc.. have 2 electrons at the last orbit. But magnetic field occurs even if a single charge moves. Why exactly 2?
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1answer
114 views
Why don’t electrons fall into the nucleus of an atom? [duplicate]
The nuclei of atoms are composed of protons and neutrons. The proton has a positive charge, and the neutron a neutral charge. Shells of electrons outside the nucleus in the atom orbit around the ...
28
votes
4answers
13k views
If an apple is magnified to the size of the earth, then the atoms in the apple are approximately the size of the original apple
Quoting from the Feynman Lectures on Physics - Vol I:
The atoms are 1 or $2 \times 10^{−8}\ \rm cm$ in radius. Now $10^{−8}\ \rm cm$ is called an angstrom (just as another name), so we say they are ...
2
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3answers
78 views
Absorption of photons
We know that whenever white light falls on an object, photons of particular wavelength(de broglie's wavelength) gets absorbed by atoms which causes excitation of electron and then electron releases ...
2
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2answers
96 views
Why are there no transitions between orthohelium and parahelium?
I know the transition rule $\Delta S = 0$. But where does that rule come from?
Is it just very unlikely that an absorbed/emitted $\gamma$ will carry the energy necessary for a spin flip?
Or is there ...
0
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3answers
53 views
Atom is not neutral? [closed]
The thing that always confused me, was how can atom be electrically neutral, if electrons are closer to observer. Well, okay, I started to read a quantum mechanics book, so to clarify: there is a big ...
2
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1answer
53 views
Does Thompson's atom model have a solid positive material, or a positive “cloud”?
I understand that the explanation of why Rutherford's experiments disproved Thompson's model is that they expected all the alpha particles to go through the space between atoms with minimum deflection....
3
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2answers
56 views
Why is the downward transition of electrons in a three level pumping scheme of laser non radiative?
Laser produces coherant monochromatic waves by stimulated emission of radiation. In the three level pumping scheme of laser the downward transition of electrons from E3 to E2 is spontaneous and from ...
2
votes
2answers
141 views
Why atom has the straight discrete energy levels? [duplicate]
Interaction between a nucleus and electrons is in gravity(not considering) and electrostatics. Due to electrostatics nucleus attracts electrons. The force that describes this process is
$$F=k\dfrac{...
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2answers
48 views
Is a boron atom isotropic in the absence of a field? If so, how can one write its electronic state?
Is a boron atom isotropic in the absence of a field? If so, how can one write its electronic state?
An atom in the absence of any field should obey a spherical symmetry (unless there's spontaneous ...
2
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1answer
81 views
If you have a single atom in a box, what state of matter would it be in?
If the walls of the box were made of a completely inert material, what state of matter would the atom be in? Or would it not have one? I realized this is a duplicate of several other questions.
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1answer
30 views
Determining excitated state of an electron of an $\rm H$ atom
Suppose we have an electron of $\rm{H}$ atom( suppose it is at 4th shell). But it can't remain in the excited state for a long time. So it can jump to 1st ,2nd or the 3rd orbital. What is the factor ...
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2answers
72 views
Commercially available material with highest density to cost ratio? [closed]
What are the top 5 commercially available materials (not limited to just the elements) with the highest density to cost ratio?
To point to an application, say that my goal was to mass produce a solid ...
4
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0answers
92 views
Why do electrons abide by Hund's rule?
Is the reason why Hund's rule exists, that when electrons are in different orbitals (such as 2px, 2py, or 2pz), they are most stable (lowest energy)?
If the purpose is stability/lowest energy, ...
2
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2answers
53 views
For a molecule, does the term 'thermal vibration' mean the same thing as 'molecular vibration'?
When speaking of a molecule, do both terms ('thermal vibration' and 'molecular vibration') describe the same thing, being the one and only periodic motion of the atoms within the molecule?
Or, are ...
5
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1answer
77 views
Can non-central hamiltonians commute with $\vec{L}^2$?
Central potentials $V(r)$ trivially commute with the operator $\vec{L}^2$ in quantum mechanics because the latter is a function of the angular coordinates $(\theta,\phi)$ only. Non-central potentials, ...
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1answer
139 views
What is the largest wavelength of a photon that can excite an atom in it's groundstate?
Let's assume we have an atom in it's ground state. That atom interacts with a single photon and get's exicited to a higher energy level. How large can the wavelength of the photon be?
I'm looking ...
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3answers
114 views
What is the largest wavelength that can excite an atom?
What is the largest wavelength that can excite an atom? Or is there even a largest wavelength?
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0answers
105 views
Why Mercury, Cadmium and Zinc has low melting and boiling points and elements next to them start melting at a bit higher temperatures?
I have been playing with online periodic table and noticed that melting/boiling points are lowest for noble gasses and non metals then it starts for metals on left and creeps from right side of the ...
0
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1answer
59 views
If an atom is in its ground state, has the atom the lower energy possible and there is its lower temperature?
"In the lowest energy state, the constituents of the atom (the nucleus and the orbiting electrons) are arranged so that the total energy in the system is minimal. This is called the ground state of ...
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1answer
119 views
Should Copper 65 and Copper 63 isotopes have a larger density than a copper 29 atom?
I was looking at the first page of a paper (see https://aip.scitation.org/doi/10.1063/1.1735598#Metrics-content for details) and I ran across something odd. According to the paper, Copper isotopes 63 ...
2
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1answer
76 views
How do scientists experimentally (this means not theoretically) determine that an atom is not bonded with any other atom?
What I do not understand is how scientists can tell whether or not an atom is bonded to another atom or all by itself. If someone can help me understand this, please do.
