Redefine a key chemical concept.

If a piece of copper falls into a glass of water, nothing happens, but if a piece of sodium falls into the water, there will be a violent chemical reaction that produces enough heat to melt the sodium. 

The essential reason for this difference is that sodium is so electronegative that it "can't wait" to give up its electrons. 

Electronegativity can be said to be one of the most important characteristics of chemical elements. 

To a large extent, they determine what elements react with and how they react, what types of chemical bonds will be formed, and what properties the resulting compounds will have. 

However, most of this knowledge applies only to chemistry under standard conditions. 

Although we already have a deep understanding of the behavior of matter at atmospheric pressure, when you think about it, this is not a typical situation at all. 

Most of the matter on Earth, as well as that of other planets, is in an astonishingly high pressure environment, such as the pressure at the center of the earth reaching almost 4 million atmospheres. 

Under high pressure, strange phenomena that violate the rules of classical chemistry begin to appear one after another. 

Marikembe electronegativity. 

Electronegativity, and the closely related concept of chemical hardness, are generally considered to be two basic chemical properties. 

The level of electronegativity reflects the tendency of atoms to produce or capture electrons in chemical reactions. 

This feature makes more sense in comparison. 

For two arbitrary elements, the greater the difference in electronegativity, the more intense their atomic reactions. 

This makes the electronegative "champion" (the most electronegative element) fluorine and the "crane tail" (the least electronegative, or the most electropositive element) cesium as the two most active elements. 

They can't wait to react, so they rarely appear in pure form in nature. 

In 1934, Robert Mulliken defined electronegativity for various atoms. 

The electronegativity of Malikembe is calculated from the ionization potential of an atom and its electron affinity. 

The former measures the difficulty of "pulling" an electron from an atom, while the latter reflects the extent to which the atom is "willing" to grab an electron from the vacuum around it. 

Half of the sum of these two values is electronegativity, and half of the difference between them is the chemical hardness of the element. 

Under standard conditions, electronegativity and chemical hardness are very similar because electron affinities tend to be very small. 

As a result, chemical hardness is usually ignored. 

But the problem is, once the pressure rises, things are different. 

Anomalies under high pressure. 

Scientists have found that many abnormal phenomena can occur under high enough pressure. 

For example, every substance turns into metal. 

Interestingly, at 2 million atmospheric pressure, the metallic sodium first becomes a dielectric and then re-metallized under greater pressure. 

Inert gases under high pressure are no longer inert, they do form compounds. 

Many elements become electronic compounds, which means that they banish electrons into lattice gaps, giving crystals special properties. 

Any two elements, even the seemingly boring sodium and chlorine in salt (NaCl), can form incredible compounds governed by some mysterious rule. 

Among these anomalies are record-breaking high-temperature superconductors. 

The team realized that it was only natural that the electronegativity of an atom would change accordingly because the pressure would affect its electronic configuration. 

However, the previously proposed definition of Malikembe electronegativity is no longer applicable under high voltage. 

They decided to study how electronegativity changes with the increase of pressure. 

Redefine electronegativity. 

The team managed to explain these strange phenomena by modifying the basic chemical concepts of electronegativity and chemical hardness. 

They modified the definition and measured the electronegativity and chemical hardness of each element in the periodic table before number 96 in the range of zero to 5 million atmospheric pressure. 

Under high pressure, the two parameters are different and have different physical meanings. 

For solid materials, chemical hardness is a band gap, which controls whether the material is a metal, a dielectric or a semiconductor. 

As for electronegativity, it means the chemical potential of electrons in atoms, that is, Fermi energy in the case of solids. 

There are two special considerations for calculating this value under high pressure. 

First of all, the pressure means that there is no vacuum, so the atomic ionization potential and the affinity for vacuum electrons mentioned in the standard definition are no longer applicable. 

Therefore, in the new definition, atoms exchange electrons with electron gases, not vacuum. 

Second, they chose to replace ionization potential and affinity with enthalpy, which is essential for making meaningful predictions under pressure. 

In determining the electronegativity of all elements under high voltage, the team faces the challenge of transcending theoretical complexity. 

The researchers recalled the difficulty of one of the experiments. 

The electronegativity of Malikembe is an attribute of an isolated atom in a vacuum, but how to put an atom under a huge pressure while still keeping it basically isolated from external influence? 

They found a trick to confine atoms to a pressure cavity made up of helium atoms. 

Helium atoms are inert and helium atoms are very small, so the pressure is uniformly distributed. 

The researchers then measured the energy, or enthalpy, of electrons leaving and adding atoms, and used these data to calculate electronegativity and chemical hardness. 

In the end, their new electronegativity and chemical hardness scale results successfully explain the astonishing phenomena of non-classical chemistry that could not be explained before. 

Give me a few examples. 

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When the pressure increases, the chemical hardness tends to decrease. 

This is interpreted as a narrowing of the band gap and pushing each element to eventually become a metal. 

A long study. 

The study was conducted on and off over a total of nearly seven years. 

It not only involves a lot of deep thinking, but also requires accurate and complex calculations. 

But the hard work paid off in the end. 

By revising these two core concepts in chemistry, the team has successfully explained a series of puzzling phenomena with a unified theoretical approach, and produced new hypotheses that have an impact on geology, planetology and other sciences.