Trade.Information

Einstein's Theory of Relativity Might Make the Element's Chemistry Nearest to a Noble Gas, Similar to Radon

Superheavy element 114 should be a metal. Controversial data from an experiment in Dubna, Russia, suggest instead that effects from Einstein's theory of relativity might make the element's chemistry closer to that of a noble gas, like radon. If the results are confirmed, it would be the most significant departure yet from the predictable patterns in the periodic table of the elements.

Uranium (element 92, for the 92 protons in its nucleus) is the element with the highest atomic number commonly found in nature. In the lab, scientists have created additional elements up to 118 (with the exception of 117).

An element's characteristic chemical reactions depend on the arrangements of its outermost electrons, and elements with the same outer electron arrangement share a column in the periodic table. Artificial elements such as 114, which was first made in the 1990s, also in Dubna, should be no exception. "Theory says that 114 ... should have properties similar to those of lead," which lies directly above it in the periodic table, says theoretical chemist Valeria Pershina of GSI, a heavy-element research center in Darmstadt, Germany.

The elements however are not identical, Pershina explains. In particular, nuclei with more protons attract electrons more strongly. Those electrons orbit faster, and according to Einstein's special theory of relativity, time for them stretches out. As a result, some of the electrons' orbits are tighter than in lighter elements, affecting that element's chemistry.

But such anomalies, which have been observed in heavy elements such as 105 and are even visible in gold, should not be so large as to threaten the element's standing in the periodic table, Pershina says.

In the current experiment, chemist Heinz Gäggeler of the Paul Scherrer Institute in Villigen, Switzerland, and his collaborators produced nuclei of element 114 with a particle accelerator at Dubna's Joint Institute for Nuclear Research. The accelerator shoots a beam of calcium nuclei onto a thin foil coated with plutonium, Gäggeler says. Some of the calcium nuclei fuse with plutonium nuclei, producing a handful of 114s per month. The nuclei zip into a container filled with argon gas, where they capture electrons and become neutral 114 atoms.

To test the element's chemistry, the researchers continually pump the argon through a tube coated inside with gold. The tube has a temperature gradient, going from 30° Celsius where the argon enters to –185°C at the other end.

Atoms of a metal such as lead would readily bind to the gold, so they would not go very far down the tube. A noble gas such as radon, on the other hand, goes happily alone and would only stick to the colder part of the tube, like your fingertip sticks to the inside of a freezer. Wherever a 114 atom lands, its nucleus will decay within seconds, releasing alpha radiation. The researchers can then detect where along the tube the atom stuck.

So far, the experiment has counted a handful of decays at the cold end but none at the warm end. This element "seems not to behave like lead but much more like a noble gas," Gäggeler says. If the results hold up, he adds, "it would be the first time that an element ... does not behave as you would naïvely expect on the basis of the rules governing the periodic table."

Pershina, however, is skeptical. Only for elements with atomic numbers in the 160s or 170s—far beyond current capabilities to produce—should relativity begin to subvert the periodic table, she says. But Gäggeler says he believes that with more data, his team will win skeptics over.

Note for Theory of Relativity
The theory of relativity, or simply relativity, refers specifically to two theories of Albert Einstein: special relativity and general relativity. However, "relativity" can also refer to Galilean relativity.

The term "theory of relativity" was coined by Max Planck in 1908 to emphasize how special relativity (and later, general relativity) uses the principle of relativity.

General relativity is a theory of gravitation developed by Einstein in the years 1907–1915. The development of general relativity began with the equivalence principle, under which the states of accelerated motion and being at rest in a gravitational field (for example when standing on the surface of the Earth) are physically identical. The upshot of this is that free fall is inertial motion: In other words an object in free fall is falling because that is how objects move when there is no force being exerted on them, instead of this being due to the force of gravity as is the case in classical mechanics. This is incompatible with classical mechanics and special relativity because in those theories inertially moving objects cannot accelerate with respect to each other, but objects in free fall do so. To resolve this difficulty Einstein first proposed that spacetime is curved. In 1915, he devised the Einstein field equations which relate the curvature of spacetime with the mass, energy, and momentum within it.

Some of the consequences of general relativity are:
Time goes more slowly at lower gravitational potentials. This is called gravitational time dilation.
Orbits precess in a way unexpected in Newton's theory of gravity. (This has been observed in the orbit of Mercury and in binary pulsars).
Even rays of light (which are weightless) bend in the presence of a gravitational field.
The Universe is expanding, and the far parts of it are moving away from us faster than the speed of light. This does not contradict the theory of special relativity, since it is space itself that is expanding.
Frame-dragging, in which a rotating mass "drags along" the space time around it.
Technically, general relativity is a metric theory of gravitation whose defining feature is its use of the Einstein field equations. The solutions of the field equations are metric tensors which define the topology of the spacetime and how objects move inertially.

Note for Radon
Radon is the chemical element that has the symbol Rn and atomic number 86. Radon is a colorless, naturally occurring, radioactive noble gas that is formed from the decay of radium. It is one of the heaviest substances that are gases under normal conditions and is considered to be a health hazard. The most stable isotope, 222Rn, has a half-life of 3.8 days and is used in radiotherapy. While having been less studied by chemists due to its radioactivity, there are a few known compounds of this generally unreactive element.

Radon is a significant contaminant that affects indoor air quality worldwide. Radon gas from natural sources can accumulate in buildings and reportedly causes 21,000 lung cancer deaths per year in the United States alone. Radon is the second most frequent cause of lung cancer, after cigarette smoking, and radon-induced lung cancer is thought to be the 6th leading cause of cancer death overall.

At standard temperature and pressure, radon forms a monoatomic gas with a density of 9.73 kg/m3, about 8 times the surface density of the Earth's atmosphere, 1.217 kg/m3, and is one of the heaviest gases at room temperature and the heaviest of the noble gases (excluding ununoctium). At standard temperature and pressure radon is a colorless gas, but when it is cooled below its freezing point (202 K ; −71 °C ; −96 °F) it has a brilliant phosphorescence which turns yellow as the temperature is lowered, and becomes orange-red at the temperatures air liquefies (below 93 K ; −180 °C). Upon condensation, radon also glows because of the intense radiation it produces.

Natural radon concentrations in Earth's atmosphere are so low that radon-rich water in contact with the atmosphere will continually lose radon by volatilization. Hence, ground water has a higher concentration of 222Rn than surface water, because the radon is continuously produced by radioactive decay of 226Ra present in rocks. Likewise, the saturated zone of a soil frequently has a higher radon content than the unsaturated zone because of diffusional losses to the atmosphere.

Radon is a health hazard as exposure can cause lung cancer - in fact it is the second major cause of lung cancer after smoking. Radon as a terrestrial source of background radiation is of particular concern because, although on average it is very rare, this intensely radioactive can be found in high concentrations in many areas of the world, where it represents a significant health hazard. Radon-222 has been classified by International Agency for Research on Cancer as being carcinogenic to humans. The contribution to background radiation from radon is so large that it received special attention in the neutrino detection experiments.

Radon commercialization is regulated, but it is available in small quantities, at a price of almost $6,000 per mililitre. Because it is also radioactive and is a relatively unreactive chemical element, radon has few uses and is seldom used in academic research.

In figure, ION RACETRACK. Calcium nuclei zip down a particle accelerator (artist's impression) toward a target material (center). Researchers fused calcium with plutonium to create element 114 and study its chemistry.