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I think you are wrong about the densest metal/substance here. A while ago I read about a substance that had been developed and it weighed over 13 pounds per cubic inch. What is that substance?
Question Date: 2019-05-20
Answer 1:

The answers there are possibly incorrect, but are still reasonable based on the lack of specificity in the question. The material (which also happens to be a metal, as asked in the linked question) with the largest measured density while also being stable under standard pressures and temperatures is indeed osmium, with a density of 22.6 g/cm3 (0.82 lb/in3). Using atomic weight (average mass of the atoms of an element, which may produce different ordering than density because of differences in atomic arrangements) as an alternative metric, plutonium is the element (also a metal) which is "heaviest" (measured). Thus, the answers to the question are correct.

However, one can also consider unstable materials. In that case, the material with the highest predicted density is hassium, at 41 g/cm3 (1.49 ln/in3).

Hassium is a radioactive synthetic element with a very short decay period ( half-lives of all isotopes are 11 ms or less) under standard conditions. Because of this and the difficulty in producing it, measurements of density have not been possible. Since hassium only sort of exists (and isn't even definitively a metal), it seems a bit of a stretch to claim that it is the correct answer to the linked question.

Neither of these materials is anywhere close to the 13 lbs/in3 (360 g/cm3)of whatever material is supposed to have been developed, and I was unable to find reports of any such substance. There are substances denser than osmium and hassium, such as neutron stars (density ~1014 g/cm3) and quark-gluon plasma (~1016 g/cm3). Those can hardly be called "metal" though, are not naturally occurring or present (for long) under common Earth conditions, and so are not relevant to the linked question. While the latter was developed on Earth (in the Large Hadron Collider), that density far exceeds the 13 lb/in3 of the current question, and so is unlikely to be the supposed developed material.

Note in italics in the above paragraphs the specification of standard temperature and pressure. All materials, even metals, can be compressed by applying a pressure. In doing so, the atoms are forced closer together, thereby increasing the density of the material (for example, aluminum under extremely high pressures and temperatures can be made much denser and stronger than the "normal" version). Thus, strictly speaking, no material has "a density", but rather "a density under certain conditions". Reported values of density can be assumed to correspond to measurements made at standard conditions (i.e., ~1 atmosphere of pressure and a temperature somewhere close to room temperature - IUPAC and NIST standards vary slightly but the difference is small enough that the effects are generally negligible), unless other conditions are specified. Whatever mystery material with a reported 13 lbs/in3 may be possible, but almost certainly requires pressures far greater than experienced on the surface of Earth.

Answer 2:

Hi Steve, great question! Unfortunately, I could not find anything on the substance you are asking about. As of now, the osmium is the most dense metal in the world with a density of 22.6 grams per cubic centimeter (0.816 lb/cubic inch). In second place is iridium, with a density of 22.4 grams per cubic centimeter (0.809 lb/cubic inch). A distinction must be made, however, between density and atomic weight. Density is measured in mass per unit volume, but atomic weight refers to the average mass of atoms of an element. In terms of atomic mass, the heaviest naturally occurring element is plutonium and in second place, uranium. It is also possible to create heavy metals synthetically; Oganesson (atomic number 118) is the heaviest element on the periodic table but it is a synthetic element and can’t be observed in nature. I did find something promising, though. Hassium, a synthetically created element with atomic number 108, is predicted to have a density of 40.7 grams per cubic centimeter (1.47 lb/cubic inch). A German research team successfully created the first 3 atoms of Hassium in 1984. Its density has not been proved, however, because it has a half live so small that it makes it difficult to study the element’s chemical properties. Overall, all of the above mentioned have densities much smaller than the one you mentioned, so perhaps it was misprinted. Thanks for your question!

Answer 3:

You are taking the answers to the previous question out of context. The scientists who responded to the previous question did so by either naming the densest element (not substance), or by naming the element with the highest atomic weight (which does not constitute density of the element's solid form). This is a logical fallacy, closely related to a strawman: the question these answers are addressing is a different question from the one that you are asking. Not all substances are composed of a single element.

Denser materials exist. Electron-degenerate matter, such as exists in the interior of Jupiter and that makes up white dwarf stars, is vastly denser than even the thirteen pounds per cubic inch that you mention, but electron degenerate matter is not a stable form of an element at less extreme conditions. A white dwarf, the collapsed core of a dead low-mass star, can have a mass comparable to that of the sun, but a volume comparable to that of the Earth.

Neutron-degenerate matter, the stuff of pulsars and other neutron stars, is denser yet: a neutron star has a mass at least 1.44 times that of the sun, but has a size comparable to a city. Finally, we don't know exactly what state matter falling into a black hole is compressed into when it reaches the center, since the theories of general relativity and quantum mechanics give different answers, but they do agree that the density that such matter would have is vastly greater yet (in fact, general relativity says it should be infinitely dense).

I don't know what material that you are referring to is (i.e. the material that has a density of 13 pounds per cubic inch). You didn't provide a source for where you read this, so I can't be certain that the material in question even exists. Assuming that it does exist, it would be approximately 360 grams per cubic centimeter, which is roughly 28 times the density of lead. The density of a white dwarf star with the mass of the sun and the volume of the Earth would be about 60 kilograms per cubic centimeter - about 170 times again as dense as the matter that you are referring to.

Answer 4:

I haven't found anything about a material on earth that weighs over 13 pounds per cubic inch [360,000 kg/cubic meter]. That would be 360 times as dense as water, which is .04 pounds per cubic inch, or 0.64 ounces per cubic inch. Osmium is 0.82 pounds per cubic inch.

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