Puzzles of the Black Widowers - By Isaac Asimov Page 0,11

I've got my peculiarities, would you say that necessarily makes me a bad chemist?'

"And he said, 'Well, let's see if you're a good chemist. I'm thinking of the name of a unique chemical element. You tell me what the element is, and why it's unique, and why I should think of it, and I'll admit you're a good chemist.'

"I said, 'But what would that have to do with my being a good chemist?' He said, 'The fact that you don't see that is a point against you. You ought to be able to reason it out, and reasoning is the prime tool of a chemist, or of any scientist. A person like you who talks about being a theoretical scientist and who therefore scorns little things like manual dexterity should have no trouble agreeing with this. Well, use your reason and tell me which element I am thinking of. You have one week from this moment; say, five P.M. next Monday; and you only have one chance. If your choice of element is wrong, there's no second guess.'

"I said, 'Professor Youngerlea, there are over a hundred elements. Are you going to give me any hints?'

" 'I already have,' he said. 'I told you it's unique, and that's all you're going to get.' And he gave me the same kind of grin I gave him at the time of the Beilstein incident."

Avalon said, "Well, young man, what happened the next Monday? Did you work out the problem?"

"It isn't next Monday yet, sir. That's coming three days from now, and I'm stuck. There's no possible way of answering. One element out of over a hundred, and the only hint is that it's unique."

Trumbull said, "Is the man honest? Granted that he is a bully and a rotter, do you suppose he is really thinking of an element and that he'll accept a right answer from you? He wouldn't declare you wrong no matter what you say, would he, and then use that as a weapon against you?"

Horace made a face. "Well, I can't read his mind, but as a scientist, he's the real thing. He's actually a great chemist and, as far as I know, he's completely ethical in his profession. What's more, his papers are marvelously well written - concise, clear. He uses no jargon, never a long word when a shorter one will do, never a complicated sentence when a simpler one will do. You have to admire him for that. So if he asks a scientific question, I think he will be honest about it."

"And you're really stuck?" asked Halsted. "Nothing comes to you."

"On the contrary, a great deal comes to me, but too much is as bad as nothing. For instance, the first thought I had was that the element had to be hydrogen. It's the simplest atom, the lightest atom, atom number one. It's the only atom that has a nucleus made of a single particle - just a proton. It's the only atom with a nucleus that contains no neutrons, and that certainly makes it unique."

Drake said, "You're talking about hydrogen-1."

"That's right," said Horace. "Hydrogen is found in nature in three varieties, or isotopes: hydrogen-1, hydrogen-2, and hydrogen-3. The nucleus of hydrogen-1 is just a proton, but hydrogen-2 has a nucleus composed of a proton and a neutron, and hydrogen-3 has one composed of a proton and two neutrons. Of course, almost all hydrogen atoms are hydrogen-1, but Youngerlea asked for an element, not an isotope, and if I say that the element hydrogen is the only one with a nucleus containing no neutrons, I'd be wrong. Just wrong."

Drake said, "It's still the lightest and simplest element."

"Sure, but that's so obvious. And there are other possibilities. Helium, which is element number two, is the most inert of all the elements. It has the lowest boiling point and doesn't freeze solid even at absolute zero. At very low temperatures, it becomes helium-II, which has properties like no other substance in the Universe."

"Does it come in different varieties?" asked Gonzalo.

"Two isotopes occur in nature, helium-3 and helium-4, but all those unique properties apply to both."

"Don't forget," said Drake, "that helium is the only element to be discovered in space before being discovered on Earth."

"I know, sir. It was discovered in the Sun. Helium can be considered unique in a number of different ways, but it's so obvious too. I don't think Youngerlea would have anything obvious in mind."

Drake said, after blowing a smoke ring and regarding it with