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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] hydrogen gas, molecular hydrogen, or simply hydrogen. It is colorless, odorless, [12] non-toxic, and highly combustible.
Technetium, with atomic number Z = 43, is the lowest-numbered element in the periodic table for which all isotopes are radioactive. The second-lightest exclusively radioactive element, promethium, has atomic number 61. [34]
In the periodic table of the elements, it is expected to be an s-block element, an alkali metal, and the first element in the eighth period. It is the lightest element that has not yet been synthesized. An attempt to synthesize the element has been ongoing since 2018 in RIKEN in Japan.
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 ...
It is a colorless, odorless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. [a] Its boiling point is the lowest among all the elements, and it does not have a melting point at standard pressures. It is the second-lightest and second most abundant element in the observable universe, after hydrogen. It ...
The first modern list of elements was given in Antoine Lavoisier's 1789 Elements of Chemistry, which contained 33 elements, including light and caloric. [49] [50] By 1818, Jöns Jacob Berzelius had determined atomic weights for 45 of the 49 then-accepted elements. Dmitri Mendeleev had 63 elements in his 1869 periodic table. Dmitri Mendeleev, 1897
Lithium and then potassium are the two lightest metallic elements. Magnesium , aluminium and titanium alloys are light metals of significant commercial importance. [ 2 ] Their densities of 1.7, 2.7 and 4.5 g/cm 3 range from 19 to 56% of the densities of other structural metals, [ 3 ] such as iron (7.9) and copper (8.9).
Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bond to form N 2, a colourless and odourless diatomic ...