Atomic Number Of Elements

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Atomic Number Of Elements

The atomic mass of an element is the average mass of the atoms of an element measured in atomic mass unit (amu, also known as daltons, D). The atomic mass is a weighted average of all of the isotopes of that element, in which the mass of each isotope is multiplied by the abundance of that particular isotope. (Atomic mass is also referred to as atomic weight, but the term 'mass' is more accurate.)

For instance, it can be determined experimentally that neon consists of three isotopes: neon-20 (with 10 protons and 10 neutrons in its nucleus) with a mass of 19.992 amu and an abundance of 90.48%, neon-21 (with 10 protons and 11 neutrons) with a mass of 20.994 amu and an abundance of 0.27%, and neon-22 (with 10 protons and 12 neutrons) with a mass of 21.991 amu and an abundance of 9.25%. The average atomic mass of neon is thus:

An important number in an element is the atomic number. This is the number of protons in each atom. Each element has a unique atomic number. Hydrogen is the first element and has one proton, so it has an atomic number of 1. Interactive periodic table with up-to-date element property data collected from authoritative sources. Look up chemical element names, symbols, atomic masses and other properties, visualize trends, or even test your elements knowledge by playing a periodic table game! The atomic number is the number of protons in the nucleus of an atom. The number of protons define the identity of an element (i.e., an element with 6 protons is a.

0.9048×19.992 amu=18.09 amu
0.0027×20.994 amu= 0.057 amu
0.0925×21.991 amu= 2.03 amu
20.18 amu

The atomic mass is useful in chemistry when it is paired with the mole concept: the atomic mass of an element, measured in amu, is the same as the mass in grams of one mole of an element. Thus, since the atomic mass of iron is 55.847 amu, one mole of iron atoms would weigh 55.847 grams. The same concept can be extended to ionic compounds and molecules. One formula unit of sodium chloride (NaCl) would weigh 58.44 amu (22.98977 amu for Na + 35.453 amu for Cl), so a mole of sodium chloride would weigh 58.44 grams. One molecule of water (H2O) would weigh 18.02 amu (2×1.00797 amu for H + 15.9994 amu for O), and a mole of water molecules would weigh 18.02 grams.

The original periodic table of the elements published by Dimitri Mendeleev in 1869 arranged the elements that were known at the time in order of increasing atomic weight, since this was prior to the discovery of the nucleus and the interior structure of the atom. The modern periodic table is arranged in order of increasing atomic number instead.

The elements of the periodic table sorted by atomic mass

click on any element's name for further information on chemical properties, environmental data or health effects.

This list contains the 118 elements of chemistry.

The chemical elements of
the periodic chart sorted by:

Atomic Mass

Name chemical elementSymbolAtomic number
- Name alphabetically1.0079HydrogenH1
- Atomic number4.0026HeliumHe2
- Symbol6.941LithiumLi3
- Atomic Mass9.0122BerylliumBe4
- Electronegativity10.811BoronB5
- Density12.0107CarbonC6
- Melting point14.0067NitrogenN7
- Boiling point15.9994OxygenO8
- Vanderwaals radius18.9984FluorineF9
- Year of discovery20.1797NeonNe10
- Inventor surname22.9897SodiumNa11
- Elements in earthcrust24.305MagnesiumMg12
- Elements in human body26.9815AluminumAl13
- Covalenz radius28.0855SiliconSi14
- Ionization energy30.9738PhosphorusP15

For chemistry students and teachers: The tabular chart on the right is arranged by Atomic mass (weight).

The lightest chemical element is Hydrogen and the heaviest is Hassium.

The unity for atomic mass is gram per mol.

Please note that the elements do not show their natural relation towards each other as in the Periodic system. There you can find the metals, semi-conductor(s), non-metal(s), inert noble gas(ses), Halogens, Lanthanoides, Actinoids (rare earth elements) and transition metals.

32.065SulfurS16
35.453ChlorineCl17
39.0983PotassiumK19
39.948ArgonAr18
40.078CalciumCa20
44.9559ScandiumSc21
47.867TitaniumTi22
50.9415VanadiumV23
51.9961ChromiumCr24
54.938ManganeseMn25
55.845IronFe26
58.6934NickelNi28
58.9332CobaltCo27
63.546CopperCu29
65.39ZincZn30
69.723GalliumGa31
72.64GermaniumGe32
74.9216ArsenicAs33
78.96SeleniumSe34
79.904BromineBr35
83.8KryptonKr36
85.4678RubidiumRb37
87.62StrontiumSr38
88.9059YttriumY39
91.224ZirconiumZr40
92.9064NiobiumNb41
95.94MolybdenumMo42
98TechnetiumTc43
101.07RutheniumRu44
102.9055RhodiumRh45
106.42PalladiumPd46
107.8682SilverAg47
112.411CadmiumCd48
114.818IndiumIn49
118.71TinSn50
121.76AntimonySb51
126.9045IodineI53
127.6TelluriumTe52
131.293XenonXe54
132.9055CesiumCs55
137.327BariumBa56
138.9055LanthanumLa57
140.116CeriumCe58
140.9077PraseodymiumPr59
144.24NeodymiumNd60
145PromethiumPm61
150.36SamariumSm62
151.964EuropiumEu63
157.25GadoliniumGd64
158.9253TerbiumTb65
162.5DysprosiumDy66
164.9303HolmiumHo67
167.259ErbiumEr68
168.9342ThuliumTm69
173.04YtterbiumYb70
174.967LutetiumLu71
178.49HafniumHf72
180.9479TantalumTa73
183.84TungstenW74
186.207RheniumRe75
190.23OsmiumOs76
192.217IridiumIr77
195.078PlatinumPt78
196.9665GoldAu79
200.59MercuryHg80
204.3833ThalliumTl81
207.2LeadPb82
208.9804BismuthBi83
209PoloniumPo84
210AstatineAt85
222RadonRn86
223FranciumFr87
226RadiumRa88
227ActiniumAc89
231.0359ProtactiniumPa91
232.0381ThoriumTh90
237NeptuniumNp93
238.0289UraniumU92
243AmericiumAm95
244PlutoniumPu94
247CuriumCm96
247BerkeliumBk97
251CaliforniumCf98
252EinsteiniumEs99
257FermiumFm100
258MendeleviumMd101
259NobeliumNo102
261RutherfordiumRf104
262LawrenciumLr103
262DubniumDb105
264BohriumBh107
266SeaborgiumSg106
268MeitneriumMt109
272RoentgeniumRg111
277HassiumHs108
DarmstadtiumDs110
CoperniciumCn112
NihoniumNh113
FleroviumFl114
MoscoviumMc115
LivermoriumLv116
TennessineTs117
OganessonOg118

Click here: for a schematic overview of the periodic table of elements in chart form

Do you need to know the weight of some molecules? Try our Molecular Weight Calculator!

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