large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb_9
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
English
12904
Throughout the 19th century, chemists did not know why so many atomic weights were whole numbers, while others weren't. They simply made their measurements and recorded what they found. For an explanation, they had to wait for a line of investigation into electricity to come to fruition. THROUGHOUT THE NINETEENTH CENTURY CHEMISTS DID NOT KNOW WHY SO MANY ATOMIC WEIGHTS WERE WHOLE NUMBERS WHILE OTHERS WERE NOT THEY SIMPLY MADE THEIR MEASUREMENTS AND RECORDED WHAT THEY FOUND FOR AN EXPLANATION THEY HAD TO WAIT FOR A LINE OF INVESTIGATION INTO ELECTRICITY TO COME TO FRUITION
thout allowing any atomic weight to be less than 1. For that reason, he set the atomic weight of oxygen at exactly 16 and in that case, the atomic weight of hydrogen had to be placed just a trifle higher than 1. The atomic weight of hydrogen became 1.008. This system was retained for nearly a century and a half. Throughout the 19th century, chemists kept on working out atomic weights more and more carefully. By the start of the 20th century, most elements had their atomic weights worked out to two decimal places, sometimes three. A number of elements had atomic weights that were nearly whole numbers on the “oxygen = 16” standard. The atomic weight of aluminum was just about 27, that of calcium almost 40, that of carbon almost 12, that of gold almost 197, and so on. On the other hand, some elements had atomic weights that were far removed from whole numbers. The atomic weight of chlorine was close to 35.5, that of copper to 63.5, that of iron to 55.8, that of silver to 107.9, and so on. N THAT CASE THE ATOMIC WEIGHT OF HYDROGEN HAD TO BE PLACED JUST A TRIFLE HIGHER THAN ONE THE ATOMIC WEIGHT OF HYDROGEN BECAME ONE POINT ZEROZERO EIGHT THIS SYSTEM WAS RETAINED FOR NEARLY A CENTURY AND A HALF THROUGHOUT THE NINETEENTH CENTURY CHEMISTS KEPT ON WORKING OUT ATOMIC WEIGHTS MORE AND MORE CAREFULLY BY THE START OF THE TWENTIETH CENTURY MOST ELEMENTS HAD THEIR ATOMIC WEIGHTS WORKED OUT TO TWO DECIMAL PLACES SOMETIMES THREE A NUMBER OF ELEMENTS HAD ATOMIC WEIGHTS THAT WERE NEARLY WHOLE NUMBERS ON THE OXYGEN EQUALS SIXTEEN STANDARD THE ATOMIC WEIGHT OF ALUMINIUM WAS JUST ABOUT TWENTY SEVEN THAT OF CALCIUM WAS ALMOST FORTY THAT OF CARBON ALMOST TWELVE THAT OF GOLD ALMOST ONE HUNDRED NINETY SEVEN AND SO ON ON THE OTHER HAND SOME ELEMENTS HAD ATOMIC WEIGHTS THAT WERE FAR REMOVED FROM WHOLE NUMBERS THE ATOMIC WEIGHT OF CHLORINE WAS CLOSE TO THIRTY FIVE POINT FIVE THAT OF COPPER SIXTY THREE POINT FIVE THAT OF IRON FIFTY FIVE POINT EIGHT THAT OF SILVER ONE O SEVEN POINT NINE AND SO ON
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