Símbolo | Co |
Número atómico | 27 |
Grupo | 9 (Familia del cobalto) |
Período | 4 |
Bloque | d |
Clasificación | Metal de transición |
Apariencia | Hard lustrous gray metal |
Color | Gris |
Número de protones | 27 p+ |
Número de neutrones | 32 n0 |
Número de electrones | 27 e- |
Fase en STP | Sólido |
Densidad | 8.9 g/cm3 |
Peso atómico | 58.9332 u |
Punto de fusión | 1768 K 1494.85 °C 2722.73 °F |
Punto de ebullición | 3200 K 2926.85 °C 5300.33 °F |
Entalpía de vaporización | 373.3 kJ/mol |
Electronegatividad (Escala de Pauling) | 1.88 |
Afinidad electrónica | 63.898 kJ/mol |
Estado de oxidación | −3, −1, 0, +1, +2, +3, +4, +5 (an amphoteric oxide) |
Energía de ionización |
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Descubrimiento y primer aislamiento | Georg Brandt (1735) |
Descubrimiento de cobalto Cobalt has been used to color glass since the Bronze Age. The word cobalt is derived from the German kobalt, from kobold meaning "goblin", a superstitious term used for the ore of cobalt by miners. The first attempts to smelt those ores for copper or silver failed, yielding simply powder (cobalt(II) oxide) instead. Because the primary ores of cobalt always contain arsenic, smelting the ore oxidized the arsenic into the highly toxic and volatile arsenic oxide, adding to the notoriety of the ore. Swedish chemist Georg Brandt (1694–1768) is credited with discovering cobalt circa 1735, showing it to be a previously unknown element, distinct from bismuth and other traditional metals. Brandt called it a new "semi-metal". He showed that compounds of cobalt metal were the source of the blue color in glass, which previously had been attributed to the bismuth found with cobalt. Cobalt became the first metal to be discovered since the pre-historical period. All other known metals (iron, copper, silver, gold, zinc, mercury, tin, lead and bismuth) had no recorded discoverers. |