A nucleus made of protons and neutrons surrounded by a cloud of electrons equal in number to the protons.

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36
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5answers
3k 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 ...
17
votes
3answers
2k 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 permeability and the permittivity of the material. But this is not what I'm interested ...
28
votes
7answers
9k 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 ...
54
votes
5answers
9k 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 ...
12
votes
8answers
1k views

Where did Schrödinger solve the radiating problem of Bohr's model?

One of the problems with Bohr's theory to describe the hydrogen atom, was that the electron orbiting around the nucleus has an acceleration. Therefore it radiates and loses energy, until it would ...
6
votes
2answers
3k 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?
3
votes
3answers
953 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 ...
8
votes
2answers
15k 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 ...
4
votes
2answers
1k 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 ...
11
votes
5answers
3k 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 ...
4
votes
3answers
521 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 ...
0
votes
1answer
175 views

How to determine the region that would contain a quantum particle

(a) A hydrogen atom is in its ground state. If space is divided into identical infinitesimal cubes, in which cube is the electron most likely to be found? If instead space is divided into 31 ...
14
votes
1answer
834 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 ...
4
votes
3answers
246 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 ...
8
votes
2answers
1k 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 ...
3
votes
4answers
2k 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 ...
1
vote
4answers
282 views

Atom Theory vs Quantum Physics

This never really occurred to me until now, so maybe it does not categorize a really important question, but according to Quantum theory anything that "is not observed is probability until it is ...
1
vote
2answers
5k views

Comparing scales of atomic level objects to scales of everyday size objects

I am trying to come up with everyday size objects comparisions of atomic scales items, e.g. if a proton probability cloud was of size basketball how far would the next atoms to it be? reason being is ...
6
votes
1answer
647 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 ...
4
votes
2answers
3k 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 ...
3
votes
5answers
996 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
2answers
5k views

What exists in the Space between atoms

Apologies to all if this has been asked before, I searched but was unable to find one similar. This is a question that has been bugging me for a while that i haven't really been able to find a ...
2
votes
1answer
686 views

What is heat and how does it effect an atom?

What happens in the atom when it gets heated or cooled and turns into gas, liquid or solid? I just want to know how does heat affect an atom.
2
votes
1answer
163 views

How much lead is there in the universe?

I know there is around 10^80 atoms in the observable universe, but is there any estimate the amount of lead in the universe (within a couple magnitudes of 10)?
2
votes
2answers
364 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?
1
vote
1answer
167 views

Atomic gravitational field?

This might be a silly question, but if every atom has its own gravitational force could atoms or molecules be attracted to each other over vast distances in the void of space if there were no other ...
1
vote
1answer
623 views

Energy required for ionizing Helium

The energy required to remove both electrons from the helium atom in its ground state is 79.0 eV. How much energy is required to ionize helium (i.e., to remove one electron)? ...
1
vote
0answers
53 views

Where do electrons get the energy to remain in orbit? [duplicate]

As we know electrons continuously revolve around the nuclus without falling in it at a high velocity beating it's force of attraction. My question is where do electrons get energy to revolve around ...
1
vote
1answer
332 views

Do atoms expand with universe? [duplicate]

Possible Duplicate: Why space expansion affects matter? Why does space expansion not expand matter? As we know, the universe is expanding, galaxies are away from each other. But what ...
0
votes
2answers
140 views

Why would an electron in an orbit be accelerating continuously and would thus radiate away its energy and fall into the nucleus in a classical model? [duplicate]

I was reading this answer by madame anna v: You are right, the planetary model of the atom does not make sense when one considers the electromagnetic forces involved. The electron in an orbit is ...
0
votes
1answer
126 views

On the atomic level, how is incandescent light structured?

I want to know from the smallest possible originating structures how the light I see generated from heat is made by atoms themselves.
0
votes
1answer
2k views

Why isn't Hydrogen's electron pulled into the nucleus? [duplicate]

Possible Duplicate: Why do electrons occupy the space around nuclei, and not collide with them? Why don’t electrons crash into the nuclei they “orbit”? From what I learned in chemistry, ...
-4
votes
2answers
254 views

What really is the smallest “mass” or “object” in the universe?

Look at this here. With respect to the sciences, the atom is obviously not the smallest piece of mass. Apparently, if people have already broken down the atom in to particles smaller than so, why ...