hafnium
Hafnium is a chemical element, its chemical symbol is Hf, its atomic number is 72, atomic weight 178.49, is a periodic family ⅣB. It is a glossy silver-gray transition metal, melting point 2233 ° C, boiling point 4602 ° C, density 13.31 g / cm 3. Dense metal hafnium nature is not active, the surface of the oxide coating layer, at room temperature is very stable, powdered hafnium easily in the air spontaneous combustion. Hafnium absorption of hydrogen is very strong, the highest can form HfH2.1. At high temperatures, hafnium reacts with nitrogen. Due to the influence of lanthanide shrinkage, the atomic radius of hafnium is almost equal to that of zirconium. Therefore, the properties of hafnium are very similar to that of zirconium, and it is difficult to separate. The most important is the double density of hafnium. Hafnium does not act with dilute hydrochloric acid, dilute sulfuric acid and strong alkali solution, but soluble in hydrofluoric acid and aqua regia. The oxidation state of hafnium is + 2, + 3, + 4, where +4 valence compound is the most stable. Hafnium Chinese pronunciation 'ㄏ ㄚ ˉ', 'hā'; or read 'ㄎ ㄜ ˉ', 'kē'. ...