Stories About Chemistry
75. When the Same Is not the Same at All
No, we have not yet done with superhigh pressure. It is about to bring us a new surprise.
The electronic environment of the nucleus is a rather strong structure. It may lose a few electrons, and then the atom becomes an ion. This process is occurring all the time during chemical interactions.
It may lose many electrons, and finally, it may lose them all so that only the “bare” nucleus is left. This is observed at million-degree temperatures, e.g., in the stars.
But here is a different riddle. Suppose the total number of electrons remains unchanged, but they arrange themselves differently in the electron shells. Such a change is bound to alter the properties of the atom, and hence of the element.
This is, so to say, the text under the illustration. Now for the illustration itself.
You should have no difficulty in picturing the potassium atom. It has four shells. The closest to the nucleus (K and L) are full: the first contains two, and the second eight electrons. Under ordinary conditions, no more electrons will go into them. But the other two shells are far from complete. The M-shell has only eight electrons (though it may have 18), and the N-shell has just been started (it has one electron), and this before the previous one is complete.
Potassium is the first atom to display inconsistent, stepwise formation of its electron shell.
But it is not difficult to imagine that instead of entering the fourth shell, potassium’s electron might continue the third one (for this shell still has ten vacancies)
Fantastic? Quite—under ordinary conditions. But superhigh pressures give rise to an extraordinary situation.
Under superhigh pressures the electron shells surrounding the nucleus contract greatly and the outer electrons can “fall” into the underlying incomplete shell.
For example, suppose the outer electron in the fourth shell of the potassium atom were imbedded in the third, making nine electrons in its M-shell.
What would this amount to? The atomic number of potassium (19) would be the same as before, and so would the number of electrons. In a word, no transmutation of elements would have occurred.
Just the same, our old friend the alkali metal potassium would no longer be our old friend. It would be a stranger with three shells instead of four and with nine electrons in its outer shell instead of one. And so the chemical properties of “neopotassium” would have to be studied anew.
What these properties would be we can only guess, because not a speck of “werewolf potassium” has ever been available for investigation.
At still higher pressures, the elements following potassium would also lose their usual aspect. Stepwise filling of electron shells, the law in the Mendeleyev Table, would here no longer be observed. As long as one shell were incomplete, the following one would remain empty.
...This would also be a periodic system, but not Mendeleyev’s. Its inhabitants (except for the elements of the first three periods) would be different. Its “alkali” metals would be copper and promethium and its “noble gases” nickel and neodynium, in which the corresponding outer shells would be completed.
This is what “deep-seated” chemistry may turn out to be! Unusual valences, strange properties, surprising compounds...
Attractive? Oh, yes! Real? Who knows... What is wanted here is again probably some “crazy” idea, since the preparation of an entirely new type of matter is involved. Even if it does exist at superhigh pressures, it should reassume the form of the conventional elements under ordinary conditions.
The question is how to preserve or “freeze" this transition. If we succeed in solving this question, we shall have in fact a new chemical science, a No. 2 chemistry.