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Hydrogen in an electrical discharge tube. Hydrogen is a colourless, odourless, and comparatively unreactive diatomic gas with a density of 8.988 × 10 −5 g/cm 3 and is about 14 times lighter than air. It condenses to a colourless liquid −252.879 °C and freezes into an ice- or snow-like solid at −259.16 °C.
Instead, due to hydrogen bonding, water is "stable, potable, odorless, benign, and... indispensable to life". [161] Less well-known of the oxides of hydrogen is the trioxide, H 2 O 3. Berthelot proposed the existence of this oxide in 1880 but his suggestion was soon forgotten as there was no way of testing it using the technology of the time. [162]
Tellurium reacts with boiling water, or when freshly precipitated even at 50 °C, to give the dioxide and hydrogen: Te + 2 H 2 O → TeO 2 + 2 H 2. [381] It reacts (to varying degrees) with nitric, sulfuric, and hydrochloric acids to give compounds such as the sulfoxide TeSO 3 or tellurous acid H 2 TeO 3 , [ 382 ] the basic nitrate (Te 2 O 4 H ...
Moreover, a hydrogen atom in a molecule can form a second, albeit weaker, bond with an atom or group of atoms in another molecule. Such bonding, "helps give snowflakes their hexagonal symmetry, binds DNA into a double helix ; shapes the three-dimensional forms of proteins ; and even raises water's boiling point high enough to make a decent cup ...
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.
These fires cannot be extinguished with water, which also react with the metals involved to give hydrogen, which is itself explosive. Noble metals, in contrast, are disinclined to react with oxygen and, for that reason (as well as their scarcity) have been valued for millennia, and used in jewellery and coins. [22]
In the early work on the chemical composition of the sun the only elements that were detected in spectra were hydrogen and various metals, [41]: 23–24 with the term metallic frequently used when describing them. [41]: Part 2 In contemporary usage all the extra elements beyond just hydrogen and helium are termed metallic.
This line has been called the amphoteric line, [2] the metal-nonmetal line, [3] the metalloid line, [4] [5] the semimetal line, [6] or the staircase. [2] [n 1] While it has also been called the Zintl border [8] or the Zintl line [9] [10] these terms instead refer to a vertical line sometimes drawn between groups 13 and 14.