large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb_218
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
English
12904
By noting the quantity of other elements that combined with a fixed mass of oxygen or of hydrogen, Dalton could work out the atomic weights of these elements as well. Dalton's idea was right, but his details were wrong in some cases. For instance, on closer examination it turned out that the water molecule was composed of 1 oxygen atom and 2 hydrogen atoms. BY NOTING THE QUANTITY OF OTHER ELEMENTS THAT COMBINED WITH A FIXED MASS OF OXYGEN OR OF HYDROGEN DALTON COULD WORK OUT THE ATOMIC WEIGHTS OF THESE ELEMENTS AS WELL DALTON'S IDEA WAS RIGHT BUT HIS DETAILS WERE WRONG IN SOME CASES FOR INSTANCE ON CLOSER EXAMINATION IT TURNED OUT THAT THE WATER MOLECULE WAS COMPOSED OF ONE OXYGEN ATOM AND TWO HYDROGEN ATOMS
rmine their relative weights; that is, how much more massive one kind of atom might be than another. For instance, he found that a quantity of hydrogen gas invariably combined with eight times its own mass of oxygen gas to form water. He guessed that water consisted of combinations of 1 atom of hydrogen with 1 atom of oxygen. (A combination of atoms is called a “molecule” from a Greek word meaning “a small mass”, and so hydrogen and oxygen atoms can be said to combine to form a “water molecule”.) [Illustration: _John Dalton_] To account for the difference in the masses of the combining gases, Dalton decided that the oxygen atom was eight times as massive as the hydrogen atom. If he set the mass of the hydrogen atom at 1 (just for convenience) then the mass of the oxygen atom ought to be set at 8. These comparative, or relative, numbers were said to be “atomic weights”, so that what Dalton was suggesting was that the atomic weight of hydrogen was 1 and the atomic weight of oxygen was 8. Y OF HIS INSTRUMENTS HE COULD HOWEVER DETERMINE THEIR RELATIVE WEIGHTS THAT IS HOW MUCH MORE MASSIVE ONE KIND OF ATOM MIGHT BE THAN ANOTHER FOR INSTANCE HE FOUND THAT A QUANTITY OF HYDROGEN GAS INVARIABLY COMBINED WITH EIGHT TIMES ITS OWN MASS OF OXYGEN GAS TO FORM WATER HE GUESSED THAT WATER CONSISTED OF COMBINATIONS OF ONE ATOM OF HYDROGEN AND ONE ATOM OF OXYGEN A COMBINATION OF ATOMS IS CALLED A MOLECULE FROM A GREEK WORD MEANING A SMALL MASS AND SO HYDROGEN AND OXYGEN ATOMS CAN BE SAID TO COMBINE TO FORM A WATER MOLECULE TO ACCOUNT FOR THE DIFFERENCE IN THE MASSES OF THE COMBINING GASES DALTON DECIDED THAT THE OXYGEN ATOM WAS EIGHT TIMES AS MASSIVE AS THE HYDROGEN ATOM IF HE SET THE MASS OF THE HYDROGEN ATOM AT ONE JUST FOR CONVENIENCE THEN THE MASS OF THE OXYGEN ATOM OUGHT TO BE SET AT EIGHT THESE COMPARATIVE OR RELATIVE NUMBERS WERE SAID TO BE ATOMIC WEIGHTS SO THAT WHAT DALTON WAS SUGGESTING WAS THAT THE ATOMIC WEIGHT OF HYDROGEN WAS ONE AND THE ATOMIC WEIGHT OF OXYGEN WAS EIGHT
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