Scientists Create Compound With a Single Element 163
rocketman768 writes "An international team of researchers including scientists at the Carnegie Institution has discovered a new chemical compound that consists of a single element: boron. Chemical compounds are conventionally defined as substances consist of two or more elements, but the researchers found that at high pressure and temperature pure boron can assume two distinct forms that bond together to create a novel 'compound' called boron boride."
Re:Eh? (Score:5, Informative)
Re:I don't understand (Score:5, Informative)
Reading the intro paragraph of the article, I have an answer.
This is an IONIC compound. Someone felt that it was an unnecessary or unimportant distinction to make.
It's the first IONIC compound to be composed of only one element.
Re:I don't understand (Score:5, Informative)
AFAIK, an allotrope is just a different spatial arrangement of atoms without any transfer of electrons. However, in this case, the arrangement is such that there is a transfer of charge from one set of atoms to another.
From TFA,
How can an element be ionic? Classical chemistry textbooks indicate that charge transfer occurs when atoms have different electronegativities and this automatically disqualifies pure elements as possible ionic phases. Boron finds a surprising solution to this problem â" its new structure contains two very different types of nanoclusters, B12 icosahedra (blue in the figure above) and B2 dumbbells (orange in the figure above). The electronic structures of these two clusters are very different â" in fact, the dependence of electronic properties on the size of the cluster is well known and is the main idea of nanotechnology. Electronegativities of the B12 icosahedra and B2 pairs are different, and this causes charge redistribution and the emergence of partial ionicity in this elemental structure.
Re:Puzzled.. (Score:5, Informative)
they're covalent, not ionic.
Re:Puzzled.. (Score:5, Informative)
Whats the difference between that, and say, N2 or O2? Aren't those also compounds of a single element?
With oxygen and nitrogen the two atoms are identical for all intents and purposes. They share electrons evenly. In this case you have boron atoms that are giving up electrons and boron atoms that are accepting them to reach a stable state. So they're behaving differently, rather than the same.
Miswritten summary (Score:5, Informative)
Frankly, the article is interesting enough without mangling it in the summary.
This is the first ionic crystal to consist of only one element. As a compound, by definition, contains two elements, it's not a compound. A boron ionic crystal is substantially different from, say, the multiple allotropes of carbon, though.
However, this is a solely theoretical crystal -- it hasn't been synthesized.
Re:I don't understand (Score:5, Informative)
Re:I don't understand (Score:5, Informative)
Because an allotrope is a different arrangement of the same element on its own.
You can find a diamond and you can also find graphite.
This would be like a graphite diamond.
Re:Oblig. Quote (Score:3, Informative)
Re:Miswritten summary (Score:4, Informative)
Actually it has been synthesized. The structure was determined using a computational method, though. In other words, they couldn't use standard techniques to interpret the x-ray diffraction data and had to use the evolutionary structure prediction method mentioned in the paper.
What I find kind of amazing is the news article mentions a Vickers hardness of 50 GPa. The journal article doesn't mention anything about that, unless it is somewhere in the supplementary materials, but anyway, if the news article estimated correctly based on the reported phase transformation pressures...that's pretty damn hard!
Except of course it isn't REALLY that simple... (Score:5, Informative)
Not to say you are at all wrong, it is a good explanation, but the distinction between 'ionic' and 'covalent' bonds is really one of a matter of degree between 2 extremes.
At the one extreme we have single element compounds like H2 or O2 in which the electronegativity of the component atoms is (by definition) equal and thus have an even charge distribution and are entirely covalent. This is the simplest case.
At the other extreme we have substances like NaCl which are made up of atoms with extremely different electronegativities. However there is no such thing as a purely 'ionic' bond. Even in an extremely polar molecule like NaCl the charge distribution isn't ENTIRELY Na+1 and Cl-1. It very nearly is, but not quite.
MOST compounds are far less clear cut. Even H2O's bonds, which are fairly polar and is composed of 2 species with very different electronegativity the bond is generally characterized as having both an ionic and a covalent character.
So, our boron boride is also going to be a compound which is not going to be entirely clearly either ionic nor covalent.
The real problem is that these terms only signify useful generalizations about how chemical species behave. While chemistry CAN be reduced to physics in a reasonably straightforward way in principle, the reality is that most of the terms and most of the ways chemists ordinarily think about chemistry is a set of 'rules of thumb' which are based as much on observation and valued as much for their general utility as they are based on precise formulations of fundamental laws and processes. Even the notion of 'compound' is really to a certain extent a convenience and necessarily gets a bit fuzzy at the 'edges'.
Re:Except of course it isn't REALLY that simple... (Score:3, Informative)
You're saying that there's no such thing as table salt. This is obviously false.
Compounds with strong ionic bonds tend to disassociate completely in water forming the constituent ions (completely being as previously indicated - not really complete).
However, the moment that they leave the water, they're back to what they were - full molecules again.