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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.

A nucleus made of protons and neutrons surrounded by a cloud of electrons equal in number to the protons. Not to be confused with ions, whose number of electrons should be different from the number of protons[1].

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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 in "orbit" around a positively charged nucleus.…
orome
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Why does space expansion not expand matter?

I have looked at other questions on this site (e.g. "why does space expansion affect matter") but can't find the answer I am looking for. So here is my question: One often hears talk of space expanding when we talk about the speed of galaxies…
SoulmanZ
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How does a knife cut things at the atomic level?

As the title says. It is common sense that sharp things cut, but how do they work at the atomical level?
wtoh
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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 getting really close to yours!" Expanding on this a…
Thomas Shields
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How can we see an atom now? What was the scale of this equipment?

I've just seen this on the news - Single Trapped Atom Captures Science Photography Competition's top prize. Credit: David Nadlinger via EPSRC I am not a Physics major but I believe I do know the basics. I have always believed that we can't really…
Hanky Panky
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What really causes 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 being related to the permeability and the permittivity of the material. But this is not what I'm interested in - I want to go deeper than that. We know…
Emitabsorb
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Is it possible to "see" atoms?

As per my knowledge, atoms are small beyond our imaginations. But there is an image on Wikipedia that shows silicon atoms observed at the surface of silicon carbide crystals. The image: How can we see these distinct atoms if they are so small?
jNerd
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What enables protons to give new properties to an atom every time one is added?

How does adding one more particle to the nucleus of an atom give that atom new properties? I can see how it changes it's mass, that's obvious... But how does it give that new atom different properties like color? A good example would be: start with…
Investor
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Has gravity ever been experimentally measured between two atoms?

Has there been any experiments, or are there any references, demonstrating gravity between atoms? If so, what are the key experiments/papers? Or if not, what is the smallest thing that has actually experimentally been shown to be affected by…
Lance Pollard
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Why are line spectra only seen in gases?

This might be a stupid question but I could not find the answer in my textbook or on the internet with a few searches. So I believe when an atomic electron moves down to a lower energy level it emits radiation in the process. However since the…
IK-_-IK
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Dumbed-down explanation how scientists know the number of atoms in the universe?

It is often quoted that the number of atoms in the universe is 10$^{70}$ or 10$^{80}$. How do scientists determine this number? And how accurate is it (how strong is the supporting evidences for it)? Is it more likely (logically >50% chance) that…
Pacerier
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Is it possible that every single isotope is radioactive, and isotopes which we call stable are actually unstable but have an extremely long half-life?

I've read that tellurium-128 has an half-life of $2.2 \times 10^{24}$ years, much bigger than the age of the universe. So I've thought that maybe every single isotope of every single atom are radioactive, and isotopes which we call "stable" are…
Quantum Force
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Can the solar system really fit in a thimble?

Almost every time somebody talks about atoms, at some point they mention something like this: If we remove the spaces between the atoms and atomic components, we can fit the solar system in a thimble. Or If we remove the spaces between the…
Adi
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To what degree of precision are atoms electrically neutral?

It is said that if, say, the electric charge is not a Lorentz invariant, neutral atoms are no longer neutral, which is not experimentally valid. I want to know to what degree of precision atoms are measured to be electrically neutral and what would…
Mohammad Javanshiry
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Are atoms unique?

Do atoms have any uniquely identifying characteristic besides their history? For example, if we had detailed information about a specific carbon atom from one of Planck's fingerprints, and could time-travel to the cosmic event in which the atom…
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