# Tag Info

35

Suppose we have two particles that attract each other. This could be an electron attracted to the nucleus by the electromagnetic force, or two nucleons attracted by the strong force, but let's keep it general for now. Suppose these two particles are separated by a distance $r$: If the particles were for example an electron and a proton there would be an ...

20

The first think you need to understand is that an atom is not 99.99% empty space. It's just a misconception which refuses to die, for several reasons: The "gee-wiz" or "far-out" factor (depending on your decade) is strong with this one. It's a convent sound-byte that is simultaneously awe-inspiring and simple to understand. We continue to depict atoms as ...

9

The protons and Neutrons in the Nucleus feel the strong nuclear force (or rather the strong force's equivalent to the van-der-Waals force). Since this force is much stronger than the electrostatic repulsion between the protons, atomic nuclei are so tiny. The electrons on the other hand do not feel the strong force at all - that's just one of their basic ...

5

This may not be a direct answer to your question - but you're wrong in your assumption. What you described is not the case every time. Matter of fact, there do exist exotic forms of matter - where there is basically no space between atomic nuclei at all; all the atoms can be squished together into a soup of protons and neutrons under the effects of extreme ...

3

The scattering length is basically a crude measure of how much interaction there is, so if you have a cold atomic gas in a trap, and it starts to interact more, then naturally atoms get kicked out of the trap by these interactions. This is then detected by enhanced loss rates. Depending on the setup you can get very weakly bound states (for example Efimov ...

2

I think your question has more to do with the electromagnetic force than the nucleus. It's not the nucleus that defines empty space in the atom so much as the electron orbitals, and a bit like the earth orbiting the sun, or, Pluto orbiting the sun - Orbits can be much much larger than what they orbit. It's electron orbits that determine both the size and, ...

2

The simplest example I can think of to illustrate this is the spectrum of the hydrogen atom. The excitation of the electron from the ground state, n = 1 produces a series of absorptions known as the Lyman series. The first line is excitation of the electron from n = 1 to n = 2, the second line is n = 1 to n = 3 and so on. But there are also absorptions due ...

2

Multielectron atom has much more complex energy spectrum than hydrogen atom. As the electrons interact with each other, the hydrogenic energy levels get shifted, and much of the hydrogen-specific degeneracy, as well as degeneracy resulting from electrons mass&charge equality, is lifted. Moreover, since the electrons do interact with each other, we can't, ...

1

The answer to your question is yes and there are experiments which use multiple excitations. A very famous one is the Lamb-Rutherford-Experiment where they could prove the existence of the lamb shift. First they excited a beam of hydrogen atoms which were in the $1S_{1/2}$ groundstate into the $2S_{1/2}$ state by bombarding them with electrons. This has a ...

1

The classical pretty shapes of orbitals like this are "hydrogen-like" orbitals. Essentially, they depict exact solutions of the Schrodinger equation for atoms with a point-nucleus and no other electrons. Atoms with multiple electrons have orbitals that are similar to those hydrogen-like orbitals, but not quite the same because of electron-electron ...

1

If you take an isolated hydrogen atom it will settle into the ground state with the spins opposed and stay there for ever. Not very exciting. However if you take a hydrogen gas and you heat it, e.g. by shining starlight on it, then the hydrogen atoms will start buzzing around and colliding with each other, and every now and then when two hydrogen atoms ...

1

(Hmpf I was almost finished when John Rennie posted his anwer .... you can see it as a supplement.) What generates absorption and emission lines are the differences in energy levels. As an example take sodium: when you heat the sodium vapor you push electrons in excited energy states, when those electrons jump from the excited in the ground state they emit ...

1

John Rennie's description of where the energy difference comes from that produces the line is of course correct. What he omitted was that it is a "forbidden transition", that is radiatively facilitated only by an extremely unlikely magnetic dipole interaction (unlike the more likely electric dipole mode which is forbidden by quantum mechanical selection ...

1

First of all I recommend you to see in Internet Richard Feynman's WHY". It is exactly what he discusses, our questions about why. An electron in an atom has two major types of energy, kinetic and potential. The first one is due to the fact that the electron performs a motion, e.g. if we calculate the average of the absolute square of the linear momentum of ...

1

All bound states (groups that are not decaying away, they're more "orbiting" in some way) of nuclei and electrons may be written as a (linear combination of) energy eigenstates – eigenstates of the Hamiltonian $H$. The Hamiltonian (energy operator) is always the same – it captures all the information about the laws of Nature and there are the same. The ...

1

I think you've misunderstood what the uncertainty principle tells us. The electrons in an atom do not have a position because they are delocalised over the whole atom. So two atoms can't behave differently because their electrons are in different positions - all atoms of the same element/isotope have thir electrons delocalised in an identical way. We can ...

1

Heat is random motion of atoms. In doppler cooling, lasers are slightly below a transition frequency when viewed in the lab frame of reference. Atoms moving faster than average toward the beam see it blue shifted just enough to absorb a photon. These atoms all receive a kick that reduces their kinetic energy. Now they are excited. They decay by emitting ...

Only top voted, non community-wiki answers of a minimum length are eligible