The new scale of electronegativity: chemical reactions

The new scale of electronegativity: chemical reactions

Martin Rahm, Assistant Professor in Physical Chemistry at Chalmers University of Technology has redefined the concept of electronegativity, with a more comprehensive scale. The concept is used to describe how strongly different atoms attract electrons.

By using electronegativity scales, it is possible to predict the approximate charge distribution in different molecules and materials, without needing complex quantum mechanical calculations or spectroscopic studies.

The new scale

Rahm’s discovery is a new scale. Rahm has undertaken the work with colleagues including a Nobel Prize-winner. It has been published in the Journal of the American Chemical Society.

Rahm explains: “The new definition is the average binding energy of the outermost and weakest bound electrons – commonly known as the valence electrons.”

He adds: “We derived these values by combining experimental photoionization data with quantum mechanical calculations. By and large, most elements relate to each other in the same way as in earlier scales. But the new definition has also led to some interesting changes where atoms have switched places in the order of electronegativity. Additionally, for some elements this is the first time their electronegativity has been calculated.”

The advantages

Although several different definitions of the concept exist, each is only able to cover parts of the periodic table. An additional challenge is how to explain why electronegativity is sometimes unable to predict chemical reactivity or the polarity of chemical bonds. This is the reasoning behind the development of the new scale.

Another advantage is how it can help to explain what happens when chemical reactions are not controlled by the process.The researchers have presented an equation where the total energy of an atom can be described as the sum of two values. One is electronegativity and the second is the average electron interaction. The two values, and their magnitude and characters of these as they change over a reaction, reveals the relative importance of electronegativity in influencing the chemical process.

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