Black Nitrogen - Periodic Table of Videos

so we've got something really exciting to tell you about a paper that came out during the lockdown it's actually physics paper but it's about a new form of nitrogen the element nitrogen and people are already calling it black nitrogen I'll explain why in a minute but before you get too excited about having your own sample it can only be made at a pressure of 1.4 million atmospheres that's 1.4 million times higher pressure than it atmospheric pressure in the Earth's surface and at a temperature a bit over 4,000 degrees Celsius what so it's not an experiment you can do in your kitchen nitrogen n2 exists as a gas at room temperature and if you cool it down he forms a liquid and so chemists everywhere are only familiar with a gas or liquid nitrogen if you call it really cold you can also get a solid but most chemists have never seen solid nitrogen phosphorous on the other hand which is in the same group of the periodic table immediately underneath nitrogen phosphorus has three different forms as a white form which is really reactive you've seen Pete burning it and then we'll watch what happens so instantaneously you can see that fantastic oxidation reaction red phosphorous which is a sort of reddish brown color and black phosphorous which I'd never seen until a couple of years ago when I was giving a lecture in the German city of Aachen and when I was a bit worried before the lecture and walking round I saw a case with a sample of black phosphorus and I photographed it for you the periodic videos viewers and as the first time for me to show you and you can see it really is black now in black phosphorus the atoms the phosphorus are arranged in rings hexagonal rings that are joined together like the wire in chicken wire but unlike chicken where they're not flat but they go up and down because of the angles between the bonds and the phosphorus nobody has ever before seen nitrogen in this form so nobody has seen nitrogen with this structure though in theory nitrogen could form that structure but usually the reason that I and everybody else teaches our students is that n2 has the strongest possible bond between two atoms a so-called triple bond and any other form of nitrogen would decompose to form into gas with a huge release of energy so you've already seen on some of our videos when reactions form and two they release a lot of energy our famous bulking dog experiment whoosh and rocket fuels you've seen our rocket engine and the decomposition of nitrogen triiodide they all form nitrogen and release energy now this experiment which was explained in the paper was performed in Germany by a group led by a scientist called Dominique laniel they have built a very special piece of apparatus that will generate really high pressures and the apparatus consists of two pieces of diamonds which are tapered so they go to a very narrow point and the end of the point is flattened when you press the fat ends of the diamonds you amplify the pressure so you can generate a really high pressure between the tips between the tips they put a very thin sheet of the metal rhenium and they drilled the tiny hole only 40 microns thinner than one of my hairs in that hole is where they did the experiment they have a machine for generating pressure they fill it by putting a very high pressure of nitrogen around the whole apparatus about 1200 atmospheres so quite high pressure of nitrogen and as they start squeezing the nitrogen solidifies and when it's solid it is not very compressible so they can ramp up the pressure very easily that's how they get the pressure but how do they heat it and the way they heat it is to shine a laser beam a very intense laser beam through the diamonds onto the sample and the laser beam can deliver a lot of energy very quickly and heat up the end too before they have melted the whole of the apparatus right and when they heat it up the nitrogen bonds get broken the atoms get really hot give out a lot of light because they're just so hot you know how red-hot things give out light and this is much hotter than red-hot when the bonds are broken they can reform in a different way and how do they form what happens what happens is that at a pressure of about 1.2 million atmospheres the nitrogen is actually black and this is the exciting thing when they heat it up at 1.4 million atmospheres it suddenly goes transparent so they have their a sample of transparent nitrogen and a really high pressure and the question is how do you find out what this transparent stuff is made of how are the nitrogen atoms arranged Martin after they've done the experiment and they've had the high pressure and the laser and everything's turned off does the nitrogen stay in a solid form once it's formed at least for the time of the experiment everything is stable how much have they made like a thimbleful or like how much do you make in this that'll avoid well you have a hole that is 40 microns in diameter and the rhenium starts at 200 microns thick and gets squashed so there's really very very little you know normally we talk about cubic centimeters or milliliters here we're talking about the Pico liter or perhaps even less so a tiny tiny amount so the question is how do you find out what it is and they had two different ways of doing it the first way is that they've taken their apparatus to a so called synchrotron this is a very large piece of equipment and electron accelerator which produces very intense pulses of x-rays and you can use those x-rays to look at the structure of crystals and the tiny piece of nitrogen transparent nitrogen they've made is a crystal what happens when they shine the x-rays onto the crystal is that the x-rays are diffracted to a series of spots rather light light is diffracted from the back of the CD or dvd from the pattern of these spots they can compute what the structure of the solid was that diffracted the x-rays have they carried the crystal from where they did the experiment to the synchrotron or do they do the experiment at the synchrotron or is the crystal stable enough that you can put it in a container and carry it around the experiments done in the synchrotron and as far as I know they take the diffraction pattern as quickly as they can after they've heated with the laser and there are some nice pictures that dominique sent to us showing the equipment's in situ at the synchrotron it looks so complicated I don't even quite know which way the beam goes but it's pretty impressive and what did the synchrotron tell them what had they created what the synchrotron told them was that the structure of the nitrogen they had formed was exactly the same structure as the structure of black phosphorus which is why they called the material BP n BP for black phosphorus and then n for nitrogen so there's no actual phosphorous in there the BP just stands for this is like black phosphorus yes precisely no phosphorous in it at all it just has the same structure some journalists who've reported it simplified it and called it black nitrogen which is a bit silly since it's transparent and the light can get through but it was black for a while and then it went transparent what's that about the solid nitrogen from which its formed is black because it has some other structure and I don't know precisely why it's black but the fact that the BP nitrogen is colorless is really interesting they believe the reason is that in black phosphorus which is really black the bonds between each phosphorus item at the same length but in the nitrogen form some of the nitrogen atoms are closer together than other ones and this means that the electrons in the black nitrogen is arranged in a different way from the electrons in black phosphorus and for physicists that's really very interesting so professor I can see what the physicists are excited just because they've seen something for the first time but is there any usefulness to this or applications like with graphene and things like that I think the answer is that there is no application for black nitrogen as it is but it might have some use because in the sense that it will allow people to understand the behavior of nitrogen and allow them to design new materials which contains some nitrogen and perhaps some phosphorus or some other element so that they can get different electronic properties but from the point of view of chemists I think it is very interesting because we as chemists usually don't think very much about high pressures for us 200 atmospheres is already a really high pressure and we never really think much about how our elements behave when there is a million atmospheres pressure and so I think what this experiment will do is make me be slightly less dogmatic when I say nitrogen only exists as n2 and for some of you who are away from school because of lockdown when you go back you can say to your teachers you wrong there isn't just n2 there's a new form that's been discovered I never tried freezing a banana [Music]

Channel: Periodic Videos

Views: 721,906

Keywords: periodic, videos, chemistry, nitrogen, black nitrogen

Id: dxPKuxrrG7A

Length: 13min 9sec (789 seconds)

Published: Sun Jul 12 2020