【改写化学书:氦化合物开启化学新领域】

【改写化学书:氦化合物开启化学新领域】

化学课上我们学过,氦气属于惰性气体,极具稳定性,没有共价键。然而,科学家已成功创造由氦、钠原子组成,萤石型结构的氦钠化合物,它必须在压力大于113GPa的高压环境才能稳定存在,将无法存在于地球上,但可存在于高压气态行星如木星和土星。这项创造不仅颠覆化学的基本假设,更开启了人类研究其它星球化学的新领域。

http://www.dailymail.co.uk/sciencetech/article-4199576/Bizarre-new-helium-compound-rewrite-science-books.html

Forget what you were taught in chemistry class: Bizarre new helium compound may rewrite science books

  • Helium was thought to be a noble gas because it was unreactive
  • But researchers have managed to create a helium sodium compound
  • The compound can only exist under high pressures such as on other planets 
  • The scientists say their work marks a 'new frontier of chemistry' 

At school you may have been taught that helium was a noble gas because it was totally unreactive.

But, new research suggests it might not be as virtuous as we first thought.

An international team of scientists has created a stable helium compound which is composed of both helium and sodium atoms, and say their discovery marks a 'new frontier of chemistry.'

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An international team of scientists have created a new compound which is made of both helium (graphic pictured) and sodium atoms

An international team of scientists have created a new compound which is made of both helium (graphic pictured) and sodium atoms

MAKING THE NEW COMPOUND

Scientists squeezed helium gas and sodium crystals at incredibly high pressure between a pair of diamonds.

The atoms bonded in a cube-shape, sharing their electrons between them.

The resulting compound is an 'electride'.

Helium is generally understood to be inert due it its extremely stable chemical configuration, and was not known to generally form bonds with other atoms.

But a team of researchers, led by Utah State University, have managed to create a thermodynamically stable compound of helium and sodium.

Not only does the discovery go against basic assumptions about chemistry, but it will also help scientists understand the high-pressure centre of gas giants such as Jupiter and Saturn.

 

'Chemistry changes when you apply high pressure, and this can be achieved inside our Earth and on different planets like Saturn,' study co-author Ivan Popov, a doctoral student at the Utah State University, told Gizmodo.

Mr Popov described the discovery, which appears in the journal Nature Chemistry, as a 'book changer'.

Noble gases, such as helium, neon, argon, krypton, xenon and radon were long believed to be totally unreactive.

This is the first time scientists have been able to make a stable compound out of helium. The new compound would not be able to exist on earth but could exist in high-pressure gaseous planets such as Jupiter and Saturn (stock image)

This is the first time scientists have been able to make a stable compound out of helium. The new compound would not be able to exist on earth but could exist in high-pressure gaseous planets such as Jupiter and Saturn (stock image)

HOW DO ATOMS BOND?

Atoms are composed of positively charged nuclei surrounded by negatively charged electrons.

The electrons are held around the nucleus in layers called shells.

Atoms bond by sharing the electrons on their outermost shells.

However, noble gases such as helium have a complete set of electrons in their outer shell.

This means they normally have little interest in bonding with other atoms.

Although xenon and argon were shown to bond with magnesium under high pressure, this is the first time scientists have been able to make a stable compound out of helium.

'It's not a real bond' in the sense of the ionic and covalent bonds you learned about in chemistry, explained Mr Popov.

'But [the helium] does stabilize the structure. If you take those helium atoms away, the structure will not be stable', he told Gizmodo.

The helium sodium compound has a fluorite-type structure and is only stable at pressures greater than 113 GPa (gigapascal).

The new compound would not be able to exist on Earth, but could exist in high-pressure gaseous planets such as Jupiter and Saturn.

The new compound would not be able to exist on Earth, but could exist in high-pressure gaseous planets such as Jupiter and Saturn (pictured)

The new compound would not be able to exist on Earth, but could exist in high-pressure gaseous planets such as Jupiter and Saturn (pictured)

Scientists believe it will give an insight into what chemistry looks like inside other planets.

'We have long suspected that a quite different chemistry, controlled by rather different if not very different rules, must exist under extreme conditions such as ultra high pressures,' Henry Rzepa, a professor at Imperial College, London, told Gizmodo.

'This [sodium-helium compound] offers a tantalising glimpse into this new frontier of chemistry', he said.

 


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