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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.
This is a list of chemical elements and their atomic properties, ordered by atomic number (Z). ... Helium: He: 4.002602(2) ...
A helium atom is an atom of the ... A state with the quantum numbers: principal quantum number ... (13) Atomic units a.u., which equals −5.806 771 ...
Helium is inert - it does not react with other substances or combust - and its atomic number is 2, making it the second lightest element after hydrogen. Rockets need to achieve specific speeds and ...
Each distinct atomic number therefore corresponds to a class of atom: these classes are called the chemical elements. [5] The chemical elements are what the periodic table classifies and organizes. Hydrogen is the element with atomic number 1; helium, atomic number 2; lithium, atomic number 3; and so on.
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
Helium 3 is rare on Earth, primarily produced by the radioactive decay of tritium, but it does reside in abundance in the lunar regolith, deposited by billions of years of solar wind.
Atomicity is the total number of atoms present in a molecule ... while its atomic weight is 15.879; [4] therefore, its atomicity ... Helium (He) 1 3 Lithium (Li) 1 4 ...