# Tag Info

37

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 ...

12

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 ...

11

First of all, this is not true that noble gases do not form any compounds -- it can be done with some chemical tricks, usually using fluorine and some hell conditions. Yet, you don't need any chemistry to detect a new element -- helium was for instance first spotted in the sunlight spectrum. The isolation can also be made by physical means only; the most ...

7

The history is summed up in http://en.wikipedia.org/wiki/Noble_gas#History . The concept of noble gas emerged from the discovery of argon. As said by mpq, the first to be seen spectroscopically was Helium. Then Argon was detected as a component of the air less reactive than nitrogen (http://en.wikipedia.org/wiki/Argon#History ).

6

I think that you are asking whether there's an example of a naturally radioactive material, or an irradiated material, whose decay is quick enough that you can prepare a sample with one set of physical and chemical properties, wait a finite amount of time, and have a sample that is visibly changed. This would require you transform a chemically significant ...

5

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 ...

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 ...

5

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 ...

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 ...

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

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

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 ...

3

The estimated fraction of lead atoms in the universe is $6 \times 10^{−11}$.

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

NO Near the big bang temperatures were high enough that nuclei were not important. The binding energies of nuclei were trivial compared to the temperature. There was a sea of (as currently understood) quarks and gluons, so nuclei may have formed for a short time, but would break apart immediately. The best understanding is that what came out was protons ...

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.

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

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 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

Certainly with a cloud chamber you can. Here is a nice video of using one: http://www.youtube.com/watch?v=Efgy1bV2aQo There are many instructions on the internet for making your own cloud chamber and observing decay of radioactive americium-241 from an ionizing smoke detector for example.

1

Neodymium magnets are not made of elemental Neodymium. They are $Nd_2Fe_{14}B$

1

There are numerous ways something can change from one element to another. Particle colliders are a good example, just like radioactive decay. We do not have the capabilities to do this for large quantities of material, like what happens in the sun.

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