Stories About Chemistry
8. How Chemists Came Across the Unexpected
You have probably read the splendid sciencefiction novel by Herbert Wells called “The War of the Worlds,” about the invasion of Earth by emissaries from Mars. You will recall that after the last Martian was killed and life on the Earth began to settle down again, the scientists, having recovered from the shocks they had undergone, hurried to study the little that was left of the unexpected visitors from the neighbouring planet. Among other things, they were interested in the mysterious black dust which the Martians used to destroy life on Earth. After several unsuccessful experiments which ended in terrible explosions, they found the illstarred substance to be a compound of the inert gas argon with some elements not yet known on Earth.
However, at the time the great writer of science fiction was putting the finishing touches to his book, chemists were absolutely certain that argon could not combine with anything under any conditions. A large number of practical experiments had brought them to this conclusion. Argon was called an inert gas. “Inert” comes from the Greek for “inactive.” Argon is a member of a whole group of chemical sloths, which also includes helium, neon, krypton, xenon and radon. In the Periodic System they form what is known as the zero group, because the valence of these elements equals zero. The atoms of the inert gases are capable neither of donating nor of accepting electrons.
What didn’t chemists do to make them react! They heated them to temperatures at which the most refractory metals would turn into boiling hot liquids; they cooled them until they became solids; they passed enormous electric discharges through them, and they subjected them to attack by the most furious chemical agents. But all in vain! Where other elements would long have surrendered and entered into chemical union, the inert gases remained impassive. “You are wasting your time,” they seemed to say to the investigator, “We have no desire to enter into any reaction. We’re above all that! And their arrogance earned them another title, that of “noble” gases. But then this title has an ironic tinge to it.
Ramsay, who discovered helium in terrestrial minerals, had reason to be proud; he had presented the world with a new chemical element which really existed. A chemical one! Sir William Ramsay would have paid dearly to make helium behave like the other inhabitants of the Periodic Table, namely, to combine with hydrogen, oxygen, or sulphur. So that esteemed professors could tell from their rostra, about the oxides and salts of helium.
But helium, the first in the group of inert gases, failed him. At the end of the last century the British scientists Ramsay and Rayleigh disovered neon and argon, krypton and xenon. Later radon closed the list of chemical sloths. They were all elements with atomic weights of their own. But honestly, one could hardly bring oneself to prefix the word “chemical”, say, to the words “element argon.”
And so scientists moved this arrogant family of noble gases to the edge of the Mendeleyev Table, adding a new section to it, which they called the zero group. And they wrote in chemical textbooks that there existed chemical elements which were unable to form compounds under any conditions.
It was quite a blow to the scientists: quite against their will, six elements fell out of the sphere of activity of chemical science.