| 单词 | cobalt |
| 释义 | cobalt(ˈkəʊbɔːlt) noun a brittle hard silvery-white element that is a ferromagnetic metal: occurs principally in cobaltite and smaltite and is widely used in alloys. The radioisotope cobalt-60, with a half-life of 5.3 years, is used in radiotherapy and as a tracer. Symbol: Co; atomic no: 27; atomic wt: 58.93320; valency: 2 or 3; relative density: 8.9; melting pt: 1495°C; boiling pt: 2928°C Word origin C17: German Kobalt, from Middle High German kobolt goblin; from the miners' belief that malicious goblins placed it in the silver ore |
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