Oxide copper, so it displaces copper (II) oxide to form zinc oxide: Apart from metals, hydrogen can also displace metal oxides to form hydrogen oxide, also known as water: Since metals that are reactive form oxides that are stable, some metal oxides must be electrolyzed to be reduced. This includes sodium oxide, potassium oxide, calcium oxide, magnesium oxide, and aluminium oxide. The oxides must be molten before immersing graphite electrodes in them: Oxides typically react with acids or bases, sometimes both. Those reacting only with acids are labeled basic oxides. Those reacting only by bases are called "acidic oxides". Oxides that
Dihydrogen bond a protic acid and the borane end is hydridic. The resulting B−HH−N attractions stabilize the molecule as a solid. In contrast, the related substance ethane, HCCH, is a gas with a boiling point 285 °C lower. Because two hydrogen centers are involved, the interaction is termed a dihydrogen bond. Formation of a dihydrogen bond is assumed to precede formation of H from the reaction of a hydride and a protic acid. A very short dihydrogen bond is observed in NaBH·2HO with H−H contacts of 1.79, 1.86, and 1.94 Å. Protonation of transition metal hydride complexes is generally thought to occur