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Atomic mass


What is meant by the atomic mass? Definition and explanation ...

The atomic mass (English atomic mass) is the mass or the weight of a single atom. As a result, the respective atomic mass value includes the sum of the atomic constituents of proton, neutron, and electron for a single atom.
Basically, a distinction is made between relative and absolute atomic mass. The absolute atomic mass is specified with any unit of measure, for example kilogram, gram or the atomic mass unit (u). For example, the weight of u (1 u) is 1.66 * 10-27kg (= 0.00000000000000000000000000166kg). In contrast, it is in the relative atomic mass by a dimensionless number. Dimensionless means that there is no set unit of measure. The relative atomic mass refers instead to 1/12 of the mass of a 12C atoms (carbon atom).
Today, the measurement of atomic masses as accurate as possible by means of mass spectrometers is possible. The reason why the values ​​of the mass numbers are almost always so crooked is due to the fact that they are only average values ​​of the atomic masses of the different isotopes. Each chemical element occurs on Earth in a different isotope ratio. For the three isotopes of hydrogen, the relations look like this: 1H (99.9%), 2H (0.01%) and 3H (10 ^ -15%). The isotope ratio is included in the calculation of the relative atomic mass, because due to the different number of neutrons, the respective hydrogen isotopes also weigh different amounts.

List of atomic masses:

ordinalChem. ElementAtomic mass (u)
1hydrogen1,008
2helium4,002
3lithium6,94
4beryllium9,012
5boron10,81
6carbon12,011
7nitrogen14,006
8oxygen15,999
9fluorine18,998
10neon20,179
11sodium22,989
12magnesium24,305
13aluminum26,981
14silicon28,085
15phosphorus30,973
16sulfur32,06
17chlorine35,45
18argon39,948
19potassium39,098
20calcium40,078
21scandium44,955
22titanium47,867
23vanadium50,941
24chrome51,996
25manganese54,938
26iron55,845
27cobalt58,933
28nickel58,693
29copper63,546
30zinc65,409
31gallium69,723
32germanium72,63
33arsenic74,921
34selenium78,96
35bromine79,904
36krypton83,798
37rubidium85,467
38strontium87,62
39yttrium88,905
40zirconium91,224
41niobium92,906
42molybdenum95,94
43technetium98,906
44ruthenium101,07
45rhodium102,905
46palladium106,42
47silver107,868
48cadmium112,411
49indium114,818
50tin118,710
51antimony121,750
52tellurium127,60
53iodine126,90
54xenon131,293
55cesium132,905
56barium137,327
57lanthanum138,905
58cerium140,116
59praseodymium140,907
60neodymium144,24
61promethium146,91
62samarium150,36
63europium151,964
64gadolinium157,25
65terbium158,925
66dysprosium162,50
67holmium164,93
68erbium167,26
69thulium168,934
70ytterbium173,04
71lutetium174,96
72hafnium178,49
73tantalum180,947
74tungsten183,84
75rhenium186,207
76osmium190,23
77iridium192,217
78platinum195,084
79gold196,966
80mercury200,59
81thallium204,38
82lead207,20
83bismuth208,980
84polonium209,98
85astatine209,987
86radon222
87francium223,019
88radium226,02
89actinium227,027
90thorium232,038
91protactinium231,035
92uranium238,02
93neptunium237,048
94plutonium244,064
95americium243,061
96Curium247,07
97Berkelium247
98californium251
99Einsteinium252
100fermium257,09
101mendelevium258
102nobelium259
103lawrencium262
104rutherfordium261,10
105Dubnium262,113
106seaborgium263,11
107Bohrium262,12
108Hassium265
109Meitnerium268
110darmstadtium281
111Roentgenium280
112Copernicium277
113Ununtrium287
114Flerovium289
115Ununpentium288
116Livermorium293
117Ununseptium292
118Ununoctium294