# Tag Info

34

Why do most metals appear silver in color, with gold being an exception? It is hardly surprising that the answer to this question relies heavily on quantum theory, but most people will be surprised to hear that the full answer brings relativistic considerations into the picture. So we are talking quantum relativistic effects. The quantum bit of the story ...

16

Yes, so far, 20 synthetic elements have been created, with atomic numbers 99 (Einsteinium) to 118 (Ununoctium). All these elements are unstable, with half-lives ranging from a year to a few milliseconds. You can find a list on wikipedia. These elements are produced in specialized nuclear reactors, by bombarding heavy elements like Uranium and Plutonium with ...

14

Iron is a "special" element because of its nuclear binding energy. The very basic idea is that when you fuse two light elements together, you get a heavier element plus energy. You can do this up to iron. Similarly, if you have a heavy element that undergoes fission and splits into two lighter elements, you also release energy. Down to iron. You can see ...

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D electrons in metal allow optical transitions in the visible regime. Visible light can be absorbed by elements, having unbound valence electrons in d shell. So Chemistry: optical d->s$^2$ transition Iron [Ar] 3d$^6$ 4s$^2$ Tin [Kr] 4d$^{10}$ 5s$^2$ 5p (full d shell) Aluminium [Ne] 3s$^2$ 3p$^1$ (is a special case: no d valence electrons, but Aluminium ...

5

Gravity is not needed in any way (it only helps to increase the pressure inside the stars but the pressure may be "mimicked" in other ways) and the energy needed for these transmutations isn't extremely high. It's just the nuclear energy conditions. See https://en.wikipedia.org/wiki/Synthesis_of_precious_metals Consequently, one may produce gold in ...

4

If by "currently" you mean right this second, then probably -- but we won't know until it works. But if you mean recently, and I'm sure people are working on more, then the answer is yes. If you look at this table, you'll see that the newest entry is 2010 for Ununseptium. So people are interested in creating new elements. As for why, my personal ...

4

I'm not sure whether this counts as an answer since it is just one more idea for a fraud, but your question is about the physics of alloying. Actually there's no need to alloy to scam. You make up the filler mostly with tungsten, but add a little pellet of platinum. Neither of these materials will rouse the authorities' suspicion, since both have ...

3

Finding a radioactive item is conceptually the same as finding a light source. You detect what it emits with a sensor that measures the angle the radiation comes from and project it back. Do this with a few detectors and find the common point. The problem comes if you can only absorb the radiation without measuring the direction. What radiation is it ...

3

The sun's spectrum is very complex, and indeed there are a lot of "lines" both light and dark (emission and absorption) amidst a sea of what looks to be continuous frequencies. Note that the atoms you study in a textbook are idealizations. In a hot object such as the sun, some photons come to us by way of atomic emissions, but the speeds of the atoms that ...

3

some teams of physicists around the world are working on achieving that. And from time to time they do. The smash large nucleus onto each other and sometimes they fuse and result in an atomic nucleus belonging to a new element. Unfortunately, these nuclei are very short lived so you cannot create a stable bulk material with them. However, it is predicted ...

3

It's not easy. However there are attempts to calculate a phase diagram of an element from first principles. For example, in this paper http://prl.aps.org/abstract/PRL/v95/i18/e185701 the solid-liquid transition of diamond is calculated. The calculation of the free energies is done with ab initio molecular dynamics. This means that the carbon nuclei are ...

3

According to this site, we have about 433 working reactors, 65 under construction, 160 planned and 323 proposed which is too many... We're consuming about 67,990 tons per year of U-238 which would probably die out soon within about 75 years. Besides fission products, spent fuel rods contain some plutonium produced by the U-238 in breeder reactors by ...

3

In fact, some nuclear theorists do believe that there will be relatively stable heavy elements, as per your point 2. The so-called Island of Stability is predicted to occur because stability is maximized at certain so-called magic numbers which correspond to especially stable isotopes when the number of protons and/or neutrons matches one of the numbers. In ...

2

Metallic hydrogen is a metal that's not found on earth (but may be present in Jupiter): http://en.wikipedia.org/wiki/Metallic_hydrogen Wether it does anything but evaporating or burning at ambient temperatures and pressures (or whatever conditions those aliens encountered in this movie), I don't know. Since metals a generally in the lower left corner of ...

2

First part: From the formula for the radius, and the fact that magnetic field is the same in both cases, you get: $$B = \frac{m_1 v_1}{q_1 r_1} = \frac{m_2 v_2}{q_2 r_2}$$ Because you don't know the velocities, you want to get them from the potential difference. You also have $$v = \sqrt\frac{2q V}{m}$$ You put that back into the first equation, and ...

2

According to the WNA site, at the current usage (68,000 tU/yr), the world's present measured resources of uranium (5.3 Mt at present spot prices and used only in conventional reactors) are enough to last for about 80 years. This represents a conservative estimate as further exploration and higher prices will yield further resources.

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The previous answers also assume we stick with current Uranium reactors. Thorium is about 4x as common as Uranium and also makes a good nuclear fuel. So far there hasn't been much research into Thorium reactors because Uranium is pretty common and reactors use so little of it (a few ton/year) that fuel availability hasn't been a major driver. Thorium has ...

2

Metallic band structure allows absorption and re-emission of light as depicted on this site. Metals are colored because the absorption and re-emission of light are dependent on wavelength. Gold and copper have low reflectivity at short wavelengths, and yellow and red are preferentially reflected. Silver has good reflectivity that does not vary with ...

1

Well, meteorite minerals like iridium and all aren't really found on Earth in appreciable quantities. What you're looking for are exotic atoms. These certainly exist, but are too unstable. And, for certain exotic atoms like onia, atomic number isn't even defined. The binding forces cannot be different since the coupling constants are...well... constant ...

1

The position of the Lanthanides and Actindes in the periodic table is due to their electronic orbital position. While the group number of an element does correlate with physical and chemical properties, it primarily informs you of the electronic configuration. In the case of elements 90-92, they have electrons in the f-orbital, so sit comfortably in the ...

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