Hydrogen compounds

[2][3] Hydrogen also forms compounds with less electronegative elements, such as metals and metalloids, where it takes on a partial negative charge.

[9] These properties may be useful when hydrogen is purified by passage through hot palladium disks, but the gas's high solubility is a metallurgical problem, contributing to the embrittlement of many metals,[10] complicating the design of pipelines and storage tanks.

The term "hydride" suggests that the H atom has acquired a negative or anionic character, denoted H−, and is used when hydrogen forms a compound with a more electropositive element.

[17] In inorganic chemistry, hydrides can also serve as bridging ligands that link two metal centers in a coordination complex.

This function is particularly common in group 13 elements, especially in boranes (boron hydrides) and aluminium complexes, as well as in clustered carboranes.

A bare proton, H+, cannot exist in solution or in ionic crystals because of its unstoppable attraction to other atoms or molecules with electrons.

Except at the high temperatures associated with plasmas, such protons cannot be removed from the electron clouds of atoms and molecules, and will remain attached to them.

However, even in this case, such solvated hydrogen cations are more realistically conceived as being organized into clusters that form species closer to [H9O4]+.