large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb_249
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
English
12904
As it turns out, all the atoms of fluorine are of the single variety ¹⁹F, while all the atoms of sodium are ²³Na. Sometimes the atomic weight of an element, as it occurs in nature, is nearly a whole number and yet it is made up of more than 1 isotope. AS IT TURNS OUT ALL OF THE ATOMS OF FLOORIN ARE OF THE SINGLE VARIETY FLORINE NINETEEN WHILE ALL THE ATOMS OF SODIUM ARE SODIUM TWENTY THREE SOMETIMES THE ATOMIC WEIGHT OF AN ELEMENT AS IT OCCURS IN NATURE IS NEARLY A WHOLE NUMBER AND YET IT IS MADE UP OF MORE THAN ONE ISOTOPE
 by Thomson and Aston to measure the atomic weight of neon._] To avoid confusion, the average mass of the isotopes that make up a particular element is still called the atomic weight of that element. The integer closest to the mass of the individual isotope is spoken of as the “mass number” of that isotope. Thus, chlorine is made up of isotopes with mass numbers 35 and 37, but the atomic weight of chlorine as it is found in nature is 35.5 (or, to be more accurate, 35.453). In the same way, ordinary lead is made up of isotopes with mass numbers 204, 206, 207, and 208, and its atomic weight is 207.19; neon is made up of isotopes with mass numbers 20, 21, and 22, and its atomic weight is 20.183, and so on. If the atomic weight of some element happens to be very close to a whole number to begin with, it may consist of a single kind of atom. For instance, the gas fluorine (chemical symbol F) has an atomic weight of nearly 19, while that of the metal sodium (chemical symbol Na) is nearly 23. AR ELEMENT IS STILL CALLED THE ATOMIC WEIGHT OF THAT ELEMENT THE ENTER CLOSEST TO THE MASS OF THE INDIVIDUAL ISOTOPE IS SPOKEN OF AS THE MASS NUMBER OF THAT ISOTOPE THUS CHLORINE IS MADE UP OF ISOTOPES WITH MASS NUMBERS THIRTY FIVE AND THIRTY SEVEN BUT THE ATOMIC WEIGHT OF CHLORINE AS IT IS FOUND IN NATURE IS THIRTY FIVE POINT FIVE OR TO BE MORE ACCURATE THIRTY FIVE POINT FOUR FIVE THREE IN THE SAME WAY ORDINARY LEAD IS MADE UP OF ISOTOPES WITH MASS NUMBERS TWO O FOUR TWO O SIX TWO O SEVEN AND TWO O EIGHT AND ITS ATOMIC WEIGHT IS TWO O SEVEN POINT ONE NINE NEEON IS MADE UP OF ISOTOPES WITH MASS NUMBERS TWENTY TWENTY ONE AND TWENTY TWO AND ITS ATOMIC WEIGHT IS TWENTY POINT ONE EIGHT THREE AND SO ON IF THE ATOMIC WEIGHT OF SOME ELEMENT HAPPENS TO BE VERY CLOSE TO A WHOLE NUMBER TO BEGIN WITH IT MAY CONSIST OF A SINGLE KIND OF ATOM FOR INSTANCE THE GAS FLORIN CHEMICAL SYMBOL F HAS AN ATOMIC WEIGHT OF NEARLY NINETEEN WHILE THAT OF THE METAL SODIUM CHEMICAL SYMBOL N A IS NEARLY TWENTY THREE
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
file
download/librilight/large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb.flac