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Helium (from Greek: ἥλιος, romanized: helios, lit. 'sun') is a chemical element; it has symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table.
Like the periodic table, the list below organizes the elements by the number of protons in their atoms; it can also be organized by other properties, such as atomic weight, density, and electronegativity. For more detailed information about the origins of element names, see List of chemical element name etymologies.
The periodic table, ... Each of these names can be further abbreviated by a one- or two-letter chemical symbol; those for hydrogen, helium, ...
The periodic table, elements being denoted by their symbols. ... Hg is the symbol for mercury (hydrargyrum in Greek); and He is the symbol for helium ...
Bracketed noble gas symbols on the left represent inner configurations that are the same in each period. Written out, these are: He, 2, helium : 1s 2 Ne, 10, neon : 1s 2 2s 2 2p 6 Ar, 18, argon : 1s 2 2s 2 2p 6 3s 2 3p 6 Kr, 36, krypton : 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 Xe, 54, xenon : 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d ...
In 1902, having accepted the evidence for the elements helium and argon, Dmitri Mendeleev included these noble gases as group 0 in his arrangement of the elements, which would later become the periodic table. [11] Ramsay continued his search for these gases using the method of fractional distillation to separate liquid air into several components.
{{Infobox element}}; labels & notes: (Image) GENERAL PROPERTIES Name Symbol Pronunciation (data central) Alternative name(s) Allotropes Appearance <element> IN THE PERIODIC TABLE Periodic table Atomic number Standard atomic weight (data central) Element category (also header bg color) (sets header bg color, over 'series='-color) Group Period ...
All 118 discovered elements are confirmed and have a formal name and symbol, as decided by IUPAC. The last four names and symbols were added on November 28, 2016. [1] [2] Currently there are no unconfirmed discoveries and all seven periods (rows) of the periodic table are completed.