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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. Each of these names can be further abbreviated by a one- or two-letter chemical symbol; those for hydrogen, helium, and lithium are respectively H, He, and Li. [6]
Most helium was formed during the Big Bang, but new helium is created through nuclear fusion of hydrogen in stars. [5] On Earth, helium is relatively rare, only occurring as a byproduct of the natural decay of some radioactive elements. [6] Such 'radiogenic' helium is trapped within natural gas in concentrations of up to seven percent by volume ...
Hydrogen: Helium: Lithium: Beryllium: Boron: ... in the noble gas group in the periodic table. [a] ... with a very similar ratio of hydrogen/helium as is observed ...
A period 4 element is one of the chemical elements in the fourth row (or period) of the periodic table of the chemical elements.The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall ...
Hydrogen: Helium: Lithium: ... The table below is a summary of the key physical properties of the group 12 elements. ... Group 12 elements are also used in ...
The most common values of atomicity for the first 30 elements in the periodic table are as follows: ... Hydrogen (H) 2 2 Helium (He) 1 3 Lithium (Li) 1 4 Beryllium ...
Hydrogen is a chemical element; it has symbol H and atomic number 1. It is the lightest element and, at standard conditions, is a gas of diatomic molecules with the formula H 2, sometimes called dihydrogen, [11] but more commonly called hydrogen gas, molecular hydrogen or simply hydrogen.
Those orange stars found to have a higher than usual concentration of lithium (such as Centaurus X-4) orbit massive objects—neutron stars or black holes—whose gravity evidently pulls heavier lithium to the surface of a hydrogen-helium star, causing more lithium to be observed. [39]