Atomic Mass Units of 19 Elements on the Periodic Table Have Changed

The Atomic Mass Units of 19 Elements Have Changed on the Periodic Table. The IUPAC has announced that some elements in the Periodic Table have gained new weights, thanks to new devices that allow a much more precise measurement of isotopes, which represent atoms with different neutron numbers in elements.
Standard atomic mass represents the average mass of an element in atomic mass units. One atomic mass unit (akb) is exactly 12/12th of a single carbon-12 (C1) atom.
To calculate the standard atomic mass of an element, scientists average the atomic masses of all stable isotopes of the element. Although all atoms of a single element have the same number of protons in their nuclei, the neutrons in their nuclei differ due to different isotopes.
For example, carbon-12 has six protons and six neutrons. A heavier element, carbon-13, contains six protons and seven neutrons. The greater the amount of isotopes, the greater the effect on the average atomic mass.
New calculations by IUPAC have updated information on elements such as gold, cadmium, arsenic, aluminum, molybdenum, selenium, and thorium.
IUPAC official Juris Meija pointed out that the akb of the element selenium has changed for the first time since 1934.
"Knowing atomic masses is very important to understand the laws of physics… A good example of this was realized in 2005 when physicists used the exact values ​​of atomic masses to test the accuracy of the E=mc^2 equation," Meija told LiveScience.
The list of elements with varying akb values ​​published by IUPAC is as follows:
Molybdenum: old value: 95.96(2) new value: 95.95(1)
Cadmium: old value: 112.411(8) new value: 112.414(4)
Selenium: old value: 78.96(3) new value: 78.971(8)
Thorium: old value: 232.038 06(2) new value: 232.0377(4)
Beryllium: old value: 9.012 182(3) new value: 9.012 1831(5)
Fluor: old value: 18.998 4032(5) new value: 18.998 403 163(6)
Aluminum: old value: 26.981 5386(8) new value: 26.981 5385(7)
Phosphorus: old value: 30.973 762(2) new value: 30.973 761 998(5)
Scandium: old value: 44.955 912(6) new value: 44.955 908(5)
Manganese: old value: 54.938 045(5) new value: 54.938 044(3)
Cobalt: old value: 58.933 195(5) new value: 58.933 194(4)
Arsenic: old value: 74.921 60(2) new value: 74.921 595(6)
Yttrium: old value: 88.905 85(2) new value: 88.905 84(2)
Niobium: old value: 92.906 38(2) new value: 92.906 37(2)
Cesium: old value: 132.905 4519(2) new value: 132.905 451 96(6)
Praseodymium: old value: 140.907 65(2) new value: 140.907 66(2)
Holmium: old value: 164.930 32(2) new value: 164.930 33(2)
Thulium: old value: 168.934 21(2) new value: 168.934 22(2)
Gold: old value: 196.966 569(4) new value: 196.966 569(5)




Source : bursadabugun

📩 26/09/2013 00:55

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