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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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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 ...
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0answers
6 views

How is the laser frequency for doppler cooling determined?

How is the laser frequency for doppler cooling determined for a certain element? Will any frequency from the absorption lines of that element work? How is the amount of redshift in the laser ...
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 ...
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2answers
40 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
35 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,...
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2answers
76 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, ...
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2answers
60 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 ...
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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/...
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2answers
55 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. ...
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4answers
170 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(...
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2answers
39 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
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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 ...
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1answer
62 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 ...
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1answer
63 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
81 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 ...
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0answers
17 views

Does a crystal only belong to a unique crystal system?

I wonder whether a specific crystal (e.g. cubic diamond) only belongs to a unique crystal system (7 in total, see the wikipedia page). The question is from an observation that the unit cell of the ...
28
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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 ...
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3answers
70 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
80 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 ...
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3answers
50 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
51 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....
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2answers
40 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
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2answers
112 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
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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 ...
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1answer
78 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
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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
66 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 ...
3
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0answers
62 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
41 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
71 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
76 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
104 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
57 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 ...
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1answer
55 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
78 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
73 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.
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2answers
53 views

Why can't we influence neutral atoms with electric fields if they have charged constituents?

I mean, I know that it's because they're neutral and therefore have a charge of zero, but since atoms have positively charged nuclei and negatively charged electrons, why can't we directly influence ...
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1answer
134 views

How is hydrogen able to emit a light spectrum with only one electron?

When light is shined through hydrogen gas, three colors of light appear. The issue I have with this is that hydrogen has one electron, meaning somehow the electron has to be emitting all three of ...
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2answers
75 views

If $2p$ is circular, why is $2p_x$ not circular and what does $x$ mean?

I was reading about atomic orbitals. From Bohr's model, electron orbitals are considered circular. But as I saw the sub-orbitals like $2p_x$, $3d_{x^2-y^2}$ I noticed something strange. These sub-...
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0answers
116 views

Why don't atoms constantly emit light? [duplicate]

We know that accelerating charged particles emit electromagnetic radiation. We also know that electrons around nucleus have an angular momentum which means that electrons are revolving around the ...
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2answers
51 views

If I would let something mix in the blender and let time go to infinity, will all molecules be separated eventually?

Just question out of curiosity. If I would let something mix in the blender and let time go to infinity, will all molecules be separated eventually, i.e. if I open up the blender it will be gas? Or ...
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2answers
96 views

Does Earth emit Gravitational waves?

We know about bohrs model and his vagaue postulate challenging Rutherford for discrete orbits and not emitting electromagnetic waves during this. Extending this idea to our solar system, does earth ...
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4answers
95 views

How can moving electrons participate in electrostatic interaction?

People say that there is an electrostatic force between electrons and atomic nuclei. However, electrostatic force applies to static charges, i.e. charges at rest. Question: How can electrostatic ...
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1answer
23 views

Is the Hartree-Fock approximation getting better and better for higher atoms?

As the atomic number $Z$ increases, is the Hartree-Fock approximation getting better and better, or worse and worse?
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0answers
38 views

Absorbing only a fraction of photon energy

Atoms have energy levels for its electrons. When there is a match between those and light photon energy, an electronic transition ocurrs. Question Why atoms can't absorb just part of a photon ...
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5answers
3k views

Is Avogadro's law applicable for atoms or just for molecules?

I notice that online definitions of this experimental law always say, molecules or atoms. From the Wikipedia article on Avogadro's Law: $${\frac {V_{1}}{n_{1}}}={\frac {V_{2}}{n_{2}}}$$ The ...
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0answers
19 views

How can I know the volume occupied by one element in a compound?

I struggle to find how to estimate the volume occupied by one atom in a compound. As an example let's take $\beta$-Ga$_2$O$_3$, since that's the material on which I work the most. The crystal ...
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0answers
95 views

Why the electrons do not fall into the nucleus of an atom? [duplicate]

If the mass of the nucleus of an atom is where most of the atom's mass is concentrated, then the nucleus should distort (or curve) the time-space of the atom creating therefore a huge gravitational ...
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2answers
124 views

Is velocity of the electron quantized in Bohr's model?

I know that angular momentum and energy of the electron is quantized in the model. When we wrote down the equations and get the velocity equation, if I am not mistaken, we find the velocity to be ...