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183 votes
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How does a knife cut things at the atomic level?

For organic matter, such as bread and human skin, cutting is a straightforward process because cells/tissues/proteins/etc can be broken apart with relatively little energy. This is because organic ...
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  • 13k
112 votes
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How can we see an atom now? What was the scale of this equipment?

The questions of whether you can detect light emitted from an (isolated) atom and whether you can resolve an atom from its neighbours are completely independent. The spacing between different atoms ...
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98 votes
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Is it possible to "see" atoms?

This entirely depends on what you mean by "see". Let me start of by noting: As per my knowledge, atoms are small beyond our imaginations No. Atoms are quite big compared to certain other things we ...
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82 votes
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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

In "back of the envelope" calculations like this, all you can really do is look at orders of magnitude. As others have pointed out, not all apples have the same size, and not all atoms have ...
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72 votes
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What enables protons to give new properties to an atom every time one is added?

You are not correct in your latter part of the analysis; the chemical properties (which is mostly what matters in ordinary matter) almost only depend on the electron shell, and in particular the ...
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47 votes
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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?

If protons decay, then what you say is true: all atomic nuclei are indeed unstable, and a so-called "stable" nucleus simply has too long a half-life for its decay to be observed. The most tightly ...
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  • 4,765
44 votes
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Has gravity ever been experimentally measured between two atoms?

Groups in Seattle, Colorado, and perhaps others managed to measure and verify Newton's inverse-square law at submillimeter distances comparable to 0.1 millimeters, see e.g. Sub-millimeter tests of ...
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41 votes
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Why isn't the color of a molecule a combination of the colors of its component atoms?

I'll do that teacher thing and turn your question around back at you. Why isn't the spectrum of the lithium atom just the spectrum of the hydrogen atom plus the spectrum of the helium atom? And, for ...
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  • 74.3k
41 votes

How did Rutherford conclude that most of the mass (as well as the positive charge) was concentrated in the nucleus?

This is a good example of how Science works. Geiger and Marsden observed that some of the alpha particles were being backscattered. This is inconceivable if the alpha particle is scattered by a ...
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38 votes

How did Rutherford conclude that most of the mass (as well as the positive charge) was concentrated in the nucleus?

Wikipedia explains this rather well but I'll pick out the relevant stuff for you. Before the Geiger–Marsden experiment, the general idea was that atoms were built of some permeable positive substrate ...
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37 votes
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Why are line spectra only seen in gases?

In liquids and solids the difference in energy between energy levels becomes very small, due to the electron clouds of several atoms bein in very close proximity of one another. These similar energy ...
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  • 1,408
35 votes

How can we see an atom now? What was the scale of this equipment?

To be fair, this is actually explained in your link. To put it simply, If you illuminate it with the right light, it starts shining so bright that a good camera can detect it. To make it work, the ...
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35 votes
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When two molecules collide, does it produce a sound?

A sound wave is a synchronised movement of millions and millions of atoms or molecules. The random collisions of atoms or molecules are not synchronised and do not produce a sound wave. A sound wave ...
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  • 35.5k
31 votes

Prove that an electron in a hydrogen atom doesn't emit radiation

You have your "prove" in the wrong place. The way to prove that ground-state electrons in hydrogen atoms don't emit radiation is the following: Construct a sample of ground-state neutral hydrogen ...
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  • 74.3k
30 votes
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As there is no specific boundary of an atom, how was Rutherford able to estimate the size of an atom?

Rutherford probably estimated the size of gold atoms as already sketched by @AndrewSteane in his comment. The density of gold is $\rho=19.3\text{ g/cm}^3$. The molar mass of gold was known from ...
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29 votes

How does Brownian motion prove the existence of atoms?

Einstein's mathematical model of brownian motion furnished strong support of the atomic model but did not furnish airtight proof of its uniqueness (that is, the nonexistence of alternative models) at ...
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27 votes

Do we really not know why atoms 'decide' to produce a photon?

Yes, in the sense that you understand the "Why does this happen?", we really don't have an answer. That an electron emits a photon is an allowed interaction in the underlying quantum (field) theory. ...
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27 votes
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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. The problem with just calling them all "molecules" and being done with it is some are uncomfortable with ...
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26 votes
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Are all atoms spherically symmetric? If so, why are atoms with half-filled/filled sub-shells often quoted as 'especially' spherically symmetric?

In general, atoms need not be spherically symmetric. The source you've given is flat-out wrong. The wavefunction it mentions, $\varphi=\frac{1}{\sqrt3}[2p_x+2p_y+2p_z]$, is in no way spherically ...
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25 votes

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?

We are never 100% certain of anything. The scientific method falsifies wrong theories, but it does not verify those we colloquially call "correct" or "true" If we tomorrow detect a normal oxygen atom ...
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  • 108k
24 votes

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

Your question starts out with questioning whether the numbers match up very well, and then you proceed to throw away all the accuracy in your numbers to demonstrate that they don't. While throwing ...
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  • 803
23 votes

How does a knife cut things at the atomic level?

It depends on what's being cut. When metal is cut, what happens is that, on a small or not so small scale, it shears. That means layers slide over each other. The mechanism by which they slide over ...
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22 votes

Why don't electrons crash into the nuclei they "orbit"?

here's an answer from Dr.Richard Feynman http://www.feynmanlectures.caltech.edu/II_01.html#Ch1-S1 You know, of course, that atoms are made with positive protons in the nucleus and with electrons ...
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22 votes
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Why is Graphene Transparent?

Graphene is only transparent because it is very thin (one atom thick). If it absorbs 2% per layer then just a few hundred layers would absorb almost all light and that would still be a very thin sheet ...
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22 votes

Why don't electrons fall or collapse around atom when an object accelerates rapidly?

At first, as others have said,- you transfer car momentum to a whole atom system, not just to some part of it,- like electrons, nucleus, etc. Second,- an electron is not something you can easily mess ...
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21 votes

Why are line spectra only seen in gases?

You see line spectra usually only in gases because there the interaction between the atoms can be neglected. In gases with high pressures you get the so-called collision broadening of the lines which ...
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20 votes

Has gravity ever been experimentally measured between two atoms?

Measure the gravitational attraction between two atoms? Heavens no. That's such a tiny, tiny attraction. The atoms will be attracted to themselves gravitationally, but only minutely. They'll be ...
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  • 39.6k
20 votes

What enables protons to give new properties to an atom every time one is added?

Also, it is obvious that adding (or subtracting) electrons does not make a difference [...] The two differences you describe between copper and zinc are in fact due to the electrons in the atoms. So ...
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  • 3,382
20 votes
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Why don't electrons fall or collapse around atom when an object accelerates rapidly?

The laws of motion you are quoting are the classical Newtonian mechanics laws. They do not hold as such at the quantum level, they are emergent for energies and distances where classical mechanics ...
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  • 223k
20 votes

Is Pauli's Exclusion Principle a restatement of what experiments have shown?

I'll take a swing at this, from the standpoint of a puzzled high schooler, which I myself was 52 years ago. Experiments showed that there were orbitals surrounding nuclei which contained not one but ...
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