"A team of researchers led by Prof Artem Oganov of Stony Brook University has shown that, under certain conditions, ordinary rock salt can take on some surprising forms that violate textbook rules of chemistry.
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,” said lead author Dr Weiwei
“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.”
NaCl turned into stable compounds of Na3Cl, Na2Cl, Na3Cl2 and NaCl7, all of which have highly unusual chemical bonding and electronic properties.
“Na3Cl has a fascinating structure. It is comprised of layers of NaCl and layers of pure sodium. The NaCl layers act as insulators; the pure sodium layers conduct electricity. Systems with two-dimensional electrical conductivity have attracted a lot of interest,” Prof Oganov said."
SciNews
