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Polonium hydride

From Wikipedia, the free encyclopedia

Polonium hydride
Structural formula of hydrogen polonide
Space-filling model of the hydrogen polonide molecule

  Polonium, Po
  Hydrogen, H
Names
Preferred IUPAC name
Polonium hydride
Systematic IUPAC name
Polane
Other names
  • Hydrogen polonide
  • Polonium dihydride
  • Dihydridopolonium
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
25163, 169602
  • [PoH2]
Properties
PoH2
Molar mass 210.998 g/mol
Melting point −35.3 °C (−31.5 °F; 237.8 K)[1]
Boiling point 36.1 °C (97.0 °F; 309.2 K)[1]
Conjugate base Polonide
Structure
Bent
Related compounds
Other anions
H2O
H2S
H2Se
H2Te
Other cations
TlH3
PbH4
BiH3
HAt
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Polonium hydride (also known as polonium dihydride, hydrogen polonide, or polane) is a chemical compound with the formula PoH2. It is a liquid at room temperature, the second hydrogen chalcogenide with this property after water. It is very unstable chemically and tends to decompose into elemental polonium and hydrogen. It is a volatile and very labile compound, from which many polonides can be derived. Additionally, it is radioactive.[2]

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Transcription

This is a balloon of Helium, and Helium is a very small gas. we use in this case to find leaks in high pressure in high vacuum operators, because it's very very small, finds the smallest, smallest holes. But just like Hydrogen, it's also very very light. And you know, in the past we used Hydrogen to fill balloons, for transport, and now you see the Goodyear Blimp, sporting occasions, filled with Helium. So Helium is probably the most unreactive of the elements. It has a mass of 4, so it weighs four times as much as a Hydrogen atom, but Hydrogen is an H2 molecule, whereas Helium exists as isolated atoms, so that the a Helium molecule weighs twice as much as Hydrogen. See here, we have a Helium filled balloon, and it's extremely light, so I'm not gonna let it go right now so I will lose it to the ceiling. So I'm just gonna put on a piece of string. tie a lead around it again. Helium can not be synthesized in nature because it is just an element. It is found as a component of natural gas in some places, particularly in the United States, because it is formed by the radioactive decay of minerals underground, and these form Helium, which is trapped with the natural gas. So here we have a Helium balloon floating, because it's displacing its volume of air, and it'll float quite nicely. It's actually quite hard to contain, so the piece of string and the heavy stand is there holding it down, because we don't really wanna lose it. If we take a balloon of another light gas, and that's Hydrogen, and we add a match to it or we set it on fire, it will burn really really quickly, and really energetically, because it makes for lots and lots of water, Hydrogen plus Oxygen. We're gonna do the same experiment now, but we're gonna do it with a Helium filled balloon, and see if that'll burn. So here we have a technical match on a stick, and we're gonna offer it out to our floating balloon of Helium. Let's see what happens this time. A little bit of a bang, but that's just bang of the gas escaping, it didn't burn. Yep, it's unreactive, it's an inert gas. The molecule is very light, so once it is in the atmosphere it will eventually go out into outer space. So that we are, in theory at least, likely to run out of Helium in eventual future. If it is just released to the atmosphere. So what I got here is a balloon of Helium, and it's really really light, and it's displacing a lot of volume, so if I let go of it it's gonna fly like a balloon. So what we're gonna do is I'm gonna hold it down here, and Neil is gonna cool it for me using some liquid Nitrogen. Now you can see Neil is using gloves, because it's very very cold. Okay, so as he cools the balloon the gasses inside are slowing down, and they take up much much less volume as we slow them down, and now you can see it's displacing less volume, so the balloon is quite happy to sit on the table. If we stop pouring the liquid Nitrogen onto it now, and watch what happens as the balloon starts to warm up again. Because the gases are gaining more energy, and they are occupying more space, and becoming more bouyant, so the Helium comes back to the ceiling, where it really wants to be. The Helium has a whole series of useful properties because it's a very light gas, if you breathe in Helium, you then start speaking like Donald Duck, in a very squeaky voice. Helium. Fantastic element. Very light, very fun. Because the speed of sound is much greater in Helium than it is in ordinary gases. It is also very useful as a liquid. It only liquifies at very low temperature. Its boiling point is -269 degrees centigrade. But if you cool things with liquid Helium, you get very strange properties, for example, some materials lose their electrical resistance. So liquid Helium is used for magnets when you need very powerful magnets, and for example, they're used magnets from magnetic resonance imaging in hospitals. If you use a vacuum pump to pump hard on the Helium, the boiling point will go even lower, and you can go to nearly two degrees absolute. And so Helium is very important for all sorts of refrigiration. Captions by www.SubPLY.com

Preparation

Polonium hydride cannot be produced by direct reaction from the elements upon heating. Other unsuccessful routes to synthesis include the reaction of polonium tetrachloride (PoCl4) with lithium aluminium hydride (LiAlH4), which only produces elemental polonium, and the reaction of hydrochloric acid with magnesium polonide (MgPo). The fact that these synthesis routes do not work may be caused by the radiolysis of polonium hydride upon formation.[3]

Trace quantities of polonium hydride may be prepared by reacting hydrochloric acid with polonium-plated magnesium foil. In addition, the diffusion of trace quantities of polonium in palladium or platinum that is saturated with hydrogen (see palladium hydride) may be due to the formation and migration of polonium hydride.[3]

Properties

Polonium hydride is a more covalent compound than most metal hydrides because polonium straddles the border between metals and metalloids and has some nonmetallic properties. It is intermediate between a hydrogen halide like hydrogen chloride and a metal hydride like stannane.

It should have properties similar to that of hydrogen selenide and hydrogen telluride, other borderline hydrides. It is expected to be an endothermic compound, like the lighter hydrogen telluride and hydrogen selenide, and therefore would decompose into its constituent elements, releasing heat in the process. The amount of heat given off in the decomposition of polonium hydride is over 100 kJ/mol, the largest of all the hydrogen chalcogenides.

It is predicted that, like the other hydrogen chalcogenides, polonium may form two types of salts: polonide (containing the Po2− anion) and one from polonium hydride (containing –PoH, which would be the polonium analogue of thiol, selenol and tellurol). However, no salts from polonium hydride are known. An example of a polonide is lead polonide (PbPo), which occurs naturally as lead is formed in the alpha decay of polonium.[4]

Polonium hydride is difficult to work with due to the extreme radioactivity of polonium and its compounds and has only been prepared in very dilute tracer quantities. As a result, its physical properties are not definitely known.[3] It is also unknown if polonium hydride forms an acidic solution in water like its lighter homologues, or if it behaves more like a metal hydride (see also hydrogen astatide).

References

  1. ^ a b Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1985). Lehrbuch der Anorganischen Chemie (in German) (102 ed.). Walter de Gruyter. p. 627. ISBN 978-3-11-017770-1.
  2. ^ Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, p. 594, ISBN 0-12-352651-5
  3. ^ a b c Bagnall, K. W. (1962). "The Chemistry of Polonium". Advances in Inorganic Chemistry and Radiochemistry. New York: Academic Press. pp. 197–230. ISBN 9780120236046. Retrieved June 7, 2012.
  4. ^ Weigel, F. (1959). "Chemie des Poloniums". Angewandte Chemie. 71 (9): 289–316. Bibcode:1959AngCh..71..289W. doi:10.1002/ange.19590710902.
This page was last edited on 27 January 2024, at 16:07
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