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Electronegativity of atoms
May/17 paper in Nature Comm. »more info

Transfer of chirality
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Imaging electrostatic field
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On-surface chemical synthesis
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Structural and Electronic Properties of Nitrogen-Doped Graphene
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Role of the electrostatic force in AFM images
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Charge transport between two molecules
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Paper in ACS Nano
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Paper in Nature Comm.
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Jun/15 The current and the force used for controlled atomic switching of silicon tetramer. »more info

O. Wichterle prize
May/15 M. Ondracek received O. Wichterle prize for outstanding young scientists at the AS CR. »more info

Electronegativity of atoms

 Scanning microscopes can determine the electronegativity of atoms

A new insight into the characterization of chemical properties of the elements has been contributed by a method of Czech and Japanese researchers, published in the prestigious journal Nature Communications. State-of-the-art scanning-probe microscopes already enable scientists to resolve individual atoms on surfaces, but thanks to the new method, they can also measure the ability of these atoms to attract electrons, i.e. their electronegativity. The new method also makes it possible to measure the variability of electronegativity of individual atoms depending on their chemical environment. This opens the way to deeper understanding of the nature of chemical bond and chemical processes on the atomic level. Such new findings could allow control of chemical reactions in catalysis or biochemistry.

The electronegativity determines, among other things, the ability of an atom to interact with its environment and create chemical bonds. Until recently, scientists have been able to quantify it only using techniques that have worked with a large ensemble of atoms. The possibility of determining the electronegativity of a given atom depending on the chemical environment has not been possible so far. This situation has changed due to the collaboration of scientists from the Institute of Physics of the Czech Academy of Sciences, the Palacký University in Olomouc and the Universities of Tokyo and Osaka.

The new method enables us, by means of atomic force microscopy, not only to determine the electronegativity of an atom on the surface of a solid, but we are also able to determine its dependence on the chemical environment of the measured atom. That was not possible before. The method is based on experimental measurements of binding energies of individual surface atoms supported by theoretical calculations. The detailed analyses showed how the chemical environment affects the electronegativity of the atom. This knowledge can be ised for targeted management of chemical reactions. This work extends the team's own research published in 2007 in the Nature magazine. The new method, however, overcomes the limitations of the original approach of chemical identification of atoms by making it possible to identify chemical elements with different electronegativity.

The work have shown that the current values of electronegativity of chemical elements are only valid for isolated atoms. Ther method allows us to determine its changes based on the chemical environment of the atom. This gives us a new, complex view of electronegativity and therefore we have to look a little differently at characters of bonds in the chemical compounds and on the chemical reactivity itself.
 
The researchers have also demonstrated a characteristic linear relationship between the binding energies of surface atoms of different elements. Thus they demonstrated experimentally the validity of the equation proposed by Nobel prize winner Linus Pauling for the polar covalent bond in the 1930s.

 

J. Onoda, M. Ondacek, P. Jelinek, Y. Sugimoto
Electronegativity determination of individual surface atoms by atomic force microscopy
Nat. Commun. 8,  15155(1) - 15155(6) (2017).