# Tag Info

2

If you treat the 1s ground state's probability distribution as a classical charge density distribution (not really accurate, but I think the simplest way to interpret the problem), then there isn't one. This state is spherically symmetric, so the electric field is always radial and depends only on the radial coordinate and not on the angular coordinates. So ...

-2

Well, to put simple, the Bohr's model of the atom was not wrong TOTALLY - it was only acceptable for the hydrogen atom. Why? Because, in reality, electrons do not travel in a circular orbit. They travel in an elliptical orbit. Bohr's model had one significant drawback - they were only a 2-D diagram of the truth. In reality the actual model of the atom is ...

0

To add to Benito Caro's amusing, evocative and quite accurate analogy. The notion you cite that atoms can't be cut died about 100 years ago. There are two reasons this idea sometimes persists in modern culture and, although wrong, used the right way, it can be useful: The classical Greek name "atom" literally means "not cut" and thus refers either to ...

4

Think of an atom as a family with cats. The husband (neutron), wife (proton) and cat (electron) live in the house (atom). It's a bit more complicated because each house can have several husbands, wives and cats, so its more like a 1960s communal house, but anyway... The electron, like a cat, is somewhere in the house but you're never quite sure where. ...

0

In a sense this is an assumption, however it's an assumption that has a basis in the history of QM at the time. I attach images of four pages from http://www.amazon.com/Einstein-Quantum-Quest-Valiant-Swabian/dp/0691168563, which I'm currently reading and recommend if you're interested in the history, that give something of the flavor. Bohr can be said to ...

0

$F_1 = F_2 = F_3$. This is essentially the superposition principle. We know that in an atom, for example, in a neutral oxygen atom there are 8 protons and 8 electrons, i.e., 8 positive charged particles and 8 negative charged particles. We know it's nucleus can only carry 8 electrons around it. Now my question is why can't it carry so many electrons, ...

0

I've no idea here you get the number of $7.37\:\mathrm{eV}$ from. The bond dissociation of a single bond in carbon can be estimated as follows. The Enthalpy of Atomisation of carbon is $+717\:\mathrm{kJ/mol}$ and a $\mathrm{mol}$ contains four bonds. Atomisation turn carbon into a mono-atomic gas, so all bonds are broken. So if we divide ...

1

One calculates the probability that the electron is inside the nucleus by integrating $\psi^*\psi$ over the volume of the nucleus. For example, the radial part of the hydrogen ground state wavefunction is $\psi=\frac{e^{-\frac{r}{a_0}}}{\sqrt{\pi a_0^3}}$, so the integral is $\frac{1}{\pi a_0^3}\int_0^b e^{-2r/a_0} 4\pi r^2 dr$. In the above, $a_0$ is ...

1

In this link you will see the radial hydrogen wavefunctions. It is only the l=0 states, S states, that have a value different than zero at r=0. The other angular momentum states get a very small contribution to the probabilities from r>0 to r=1 fermi ( the charged radius of the proton) as 1 fermi is of order 10^-15meters, and the probability is the ...

1

It has been shown experimentally that the formation of H2 can happen in the presence of free electrons: so a photon is emitted in this two step process, taking energy away . Note that this is for low densities. The three body process in the answer by John dominates with increasing density, as discussed in the link.

1

Two isolated hydrogen atoms cannot form an $H_2$ molecule for the simple reason that they have too much energy. Any system formed from the two atoms will have an energy greater than the dissociation energy of $H_2$ so no bound state will be formed. Observation tells us that the process must happen because there is a lot of $H_2$ around. It happens when ...

0

The type of interaction depends on the energy of the photon, based on the Klein-Nishina formula. From Wikipedia: Very low energy photons (visible light; as long as the photon energy is much less than the mass energy of the particle, i.e. Compton wavelength) yields Thompson scattering, which is elastic scattering with electrons. Low energy photon (a few ...

3

Does a proton have a "bandgap"? If yes, what happens when a photon is absorbed by a proton? For single protons, as in a plasma , there exists Compton scattering . The photon transfers part of its energy to the proton and scatters off at a lower energy/frequency, the proton taking up the energy-momentum balance. This is a continuous spectrum, from very ...

3

A system can absorb a photon if the energy of the photon matches an excitation in the system. So the hydrogen atom can absorb a photon if its energy matches one of the frequencies in the hydrogen spectral series. A proton is a composite object and it does have a spectral series. However the excited states of the proton involve rearrangements of the energy ...

2

Bohr's atom became famous for reproducing the Rydberg formula for spectral lines of hydrogen, which Rydberg presented in 1888 and published the next year. Bohr remarked that it was Rydberg's switching from wavelengths to wavenumbers that allowed him to make the discovery. His inspiration came from Balmer's 1885 formula, which was a particular case, and had ...

1

A good starting point would be the series of papers by Bohr, starting with "On the constitution of atoms and molecules" Philos. Mag. 26, 1 (1913) and checking the references therein.

2

Sure, it's been done for a long time. Google "atomic force microscopy". And click on images to see lots of pictures of individual atoms/molecules/etc, e.g., http://iopscience.iop.org/0953-8984/labtalk-article/48480

4

Although not a complete answer, one place to start is with the coldest naturally occurring place in the universe, which is the Boomerang Nebula, a planetary nebula that is around 1 K. As best as I can tell, this cooled below the CMB temperature simply by adiabatic expansion, and is insulated in its interior from CMB heating. Is this a feasible way to get to ...

4

The options 1,2 are actually physically identical because the electrons are identical particles. Once we have two electrons, we can't say which of them is "Paul" and which of them is "Peter". When the addition is slow etc., the option 1=2 violates the conservation law for the angular momentum. So it is indeed 3 that has to happen: the ion will refuse to ...

0

Observables like quantised energy levels and quantised angular momentum of an atom are obtained by finding eigensolutions of the Schrödinger Equation (here for the Hydrogen atom). Separation into three parts allows to obtain the Colatitude and Azimuthal equations which allows to calculate the quantised angular momentum of the hydrogen atom, giving rise to ...

0

Compared to other answers, I would say that two atoms can definitely touch each other - this is why solid matter is "stiff" (minimum of van der Waals interaction is of the order of radius of an atomic cloud). The atoms can even overlap and they often do, say excited to a Rydberg state. In the latter case, the cloud of electrons encompasses other neutral ...

1

It depends on what you want how you choose the polarization of the light. The polarization of your light determines the recoil of your electron and your ion. In photoelectron vmi you would like to see the angular distribution of how the electron detaches from the molecule, so you should select the polarization of your light such that the velocity vector of ...

1

Spin and orbital angular momentum are two different things, as already pointed out in Aniket's answer, but there is a good reason why we still call spin a "spin". This is because the Einstein-de Haas-Richardson experiment shows that electron spin is indeed of the nature of an angular momentum, although not exactly due to a "spinning electron". In fact, ...

1

In quantum mechanics and particle physics, spin is an intrinsic form of angular momentum carried by elementary particles, composite particles (hadrons), and atomic nuclei. Spin is one of two types of angular momentum in quantum mechanics, the other being orbital angular momentum. The orbital angular momentum operator is the quantum-mechanical counterpart to ...

-2

There is a very interesting Am J Phys paper by Ohanian, titled "What is spin?". You can find free PDF copies on google, in case you don't have academic access. He points out that ALL forms of angular momentum, even spin, arise from linear momentum via the relationship $\vec r \times \vec p$. In other words, even spin is orbital angular momentum. This is ...

0

So no it is not possible to cut a nucleus or an atom in two, it is not even possible for two atoms to even touch because of electrostatic forces between the atoms. The electrons of both atoms will make two atoms strongly repel at some distance. At normal or usual distances, I should say, two atoms will barely have an effect on one another because the ...

1

If your photon has not enough energy to excite the electron then it will just not be absorbed and will pass by, and if you have an electron with an excess energy, it will be absorbed and a photon with the excess energy will be automaticaly emitted and the electron will jump to an excited state. So yeah in your case, you might have a photon with \$0.1 \space ...

-1

Frequency of anything is infinitely variable up to the point of fusion. And then again Infinitely variable to to the next densest element order of matter. frequency of anything cannot be truly calculated as gravitational forces from its most central particle outward lowers in destiny Infinitely as well from one state of matter to the next. The best one can ...

0

In addition to these two excellent answers I'd like to point out that the deceptively smooth surfaces of orbital graphical representations found in text books and web pages, like this excellent rendition of a 2p orbital, below are surfaces where the electron probability density is the same. In no way do they represent paths or 'orbits'.

5

As usual, you can re-express the wave-function in momentum space (it's just a Fourier transform away from the spacial wave-function for bound state which is really nice). But that does not tell you how the electron moves anymore than the spacial wave function tells you where it is. Instead, it tells you the probability distribution function for results of ...

-1

The lobes are regions where you have a non-zero probability of finding an electron. These regions have varying shapes for different types of orbitals. It wouldn't make sense to think that orbitals are actually paths of some sort, where electrons whizz around. You'll know this is wrong if you try to understand the uncertainty principle. The uncertainty ...

2

The question is within a Bohr model of an atom, and the Bohr model worked well for the hydrogen atom by postulating fixed orbits, but it is not the real description of what happens at the atomic dimensions. The real description for the hydrogen atom is given by the solutions for the hydrogen potential of the Schrödinger equation with the postulate of the ...

0

There are many ways... Due to their variable oxidation state, due to the strong nuclear force, and poor shielding effect. Electrons don't collide (unless they are subjected to very high velocity). They usually repel. But this repulsion force can be cancelled if the nuclear force is too high. Hence they be together. In the case of variable oxidation state, ...

3

I will try to address the points you have made in your question, one by one. First, what are electrons? Thanks to @CuriousOne, electrons are best treated as perturbations in a quantum field, which is explained by quantum-electrodynamics. In the Standard Model, they are considered elementary particles of the 1st generation lepton family with a mass 1/1836 ...

Top 50 recent answers are included