Mock atoms prove attractive: Researchers added first pseudo atoms to electronegativity scale

Jan 06, 2012
A Whiteside, SS Xantheas, and M Gutowski: "Is Electronegativity a Useful Descriptor for the Pseudo-Alkali Metal NH4?" Chemistry: A European Journal 17:13197-13205. Credit: Wiley-VCH Verlag GmbH & Co. KGaA. Reproduced with permission.

(PhysOrg.com) -- When studying an atom's ability to attract nearby electrons, scientists rely on electronegativity scales, which describe each atom's ability to pull in these negatively charged particles. But what about pseudo-atoms, a.k.a. those molecular fragments that don't change much in various environments and are considered to behave like atoms? Scientists at Pacific Northwest National Laboratory and Heriot-Watt University in Scotland put the tetrahedral ammonium radical, made from a nitrogen atom and four hydrogen atoms, on the electronegativity scale. It has the same attractive force as potassium and has the same size as an atom of rubidium.

Electron attraction and repulsion determine how atoms and pseudo-atoms behave in different environments. This study provides scientists with the information they need to better predict, manipulate and control those behaviors, whether in batteries for or catalysts for bio-fuel production.

This study began when Alexander Whiteside, a student at Heriot-Watt University, came to PNNL as part of the 2008 Summer Research Institute for Interfacial and Condensed Phase Physics. During that summer visit, Whiteside, his advisor Maciej Gutowski, and Laboratory Fellow Sotiris Xantheas started to determine the electronegativity of the ammonium radical.

The team calculated the electronic structure of the neutral ammonium molecule, NH4, and its positive and negative ions. Next, they computed the properties of ammonium complexes, specifically combining ammonium with astatine or selected borohydrides; the latter are promising materials for .

For bio-fuel production, this study provides scientists with the information they need to better predict, manipulate and control the behaviors of atoms and pseudo-atoms.

"These results clarified the properties of NH4 and placed it in the proper scale compared to the alkali metals," said Xantheas. "In comparison with alkali atoms, ammonium's electronegativity punches above its effective cationic radius. Nobody had really put it into the scale yet. This study did just that."

The results graced the cover of Chemistry: A European Journal and were highlighted in the Royal Society of Chemistry's Chemistry World.

"Past generations of physical and theoretical chemists were intrigued by the properties ammonium. Alex was standing on the shoulders of giants—Berzelius, Pauling, Mulliken, Herzberg—whose pictures are highlighted in the cover of the journal, while Sotiris and I helped him to keep his balance," joked Gutowski.

"This work opens up the opportunity to developing a comprehensive view on other pseudo-alkali metal species, pseudo-halogens and other pseudo-atoms" says Alexander Boldyrev of Utah State University.

Indeed, the team is expanding their study to the properties of the nearly ubiquitous hydronium and methyl groups, which contain a single oxygen or carbon atom and three . In addition, they are examining cyanide, a carbon and combination that could provide new insights into that pseudo-atom's behavior.

Explore further: Spinach could lead to alternative energy more powerful than Popeye

More information: Whiteside A, SS Xantheas, and M Gutowski. 2011. "Is Electronegativity a Useful Descriptor for the Pseudo-Alkali Metal NH4?" Chemistry: A European Journal 17:13197-13205. DOI:10.1002/chem.201101949

Related Stories

A New Type of Molecule

Jun 21, 2010

(PhysOrg.com) -- A Rydberg atom is one with an electron that spends most of its time far from the nucleus. Rydberg atoms, which are normally artificially produced, can have dimensions thousands of times larger ...

Iodate refuses to intimidate

Nov 08, 2011

Like a bull in a china shop, a massive, iodine-based ion called iodate should disrupt the surrounding water molecules until it is forcibly expelled. However, it doesn't. This disconnect between the molecule's ...

New Direction for Hydrogen Atom Transfers

Oct 19, 2005

In the annals of chemistry, there are many examples of hydrogen atoms moving from metals to carbon atoms. But no one has ever directly observed the reverse reaction — hydrogen atoms moving from carbon to a metal — until ...

Resolving water's electrical properties

May 18, 2011

An old confusion about the electrical properties of water's surface has ended, thanks to scientists at Pacific Northwest and Lawrence Livermore National Laboratories. The conflict arose because two types of ...

Recommended for you

A new approach to creating organic zeolites

15 minutes ago

Yushan Yan, Distinguished Professor of Engineering at the University of Delaware, is known worldwide for using nanomaterials to solve problems in energy engineering, environmental sustainability and electronics.

A tree may have the answers to renewable energy

19 hours ago

Through an energy conversion process that mimics that of a tree, a University of Wisconsin-Madison materials scientist is making strides in renewable energy technologies for producing hydrogen.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

that_guy
not rated yet Jan 06, 2012
I think this research will have a bigger foundational impact on chemistry than the authors lead you to believe. bravo to the researchers.