Road salt and table salt seem like pretty ordinary substances, but according to recent research, at 200,000 atmospheres, they can violate known rules of chemistry. From ScienceDaily:
“We found, at low pressures achievable in the lab, perfectly stable compounds that contradict the classical rules of chemistry. If you apply the rather modest pressure of 200,000 atmospheres — for comparison purposes, the pressure at the center of the Earth is 3.6 million atmospheres — everything we know from chemistry textbooks falls apart.”
Standard chemistry textbooks say that sodium and chlorine have very different electronegativities, and thus must form an ionic compound with a well-defined composition. Sodium’s charge is +1, chlorine’s charge is -1; sodium will give away an electron, chlorine wants to take an electron. According to chemistry texts and common sense, the only possible combination of these atoms in a compound is 1:1 — rock salt, or NaCl.
“We found crazy compounds that violate textbook rules — NaCl3, NaCl7, Na3Cl2, Na2Cl, and Na3Cl,” says Weiwei Zhang, the lead author and visiting scholar at the Oganov lab and Stony Brook’s Center for Materials by Design, directed by Oganov. “These compounds are thermodynamically stable and, once made, remain indefinitely; nothing will make them fall apart. Classical chemistry forbids their very existence. Classical chemistry also says atoms try to fulfill the octet rule — elements gain or lose electrons to attain an electron configuration of the nearest noble gas, with complete outer electron shells that make them very stable. Well, here that rule is not satisfied.”
Chemists, what make you of all this? Hype or help?
Note: The findings may be relevant to planetary sciences, where “high pressure phenomena abound.”