Metals high up in the reactivity series cannot be obtained by heating with carbon because they have a higher affinity for oxygen than carbon. These metals, including sodium, magnesium, and calcium, are obtained by electrolytic reduction, such as the electrolysis of their molten chlorides.
Why can’t metals high up in the reactivity series be obtained by heating their oxides with carbon, and how are metals like sodium, magnesium, and calcium obtained from their compounds?
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Metals high up in the reactivity series, like sodium, magnesium, and calcium, cannot be obtained by heating their oxides with carbon because these metals are more reactive than carbon. Carbon is unable to displace these metals from their oxides in typical reduction reactions. Instead, these metals are obtained through electrolytic reduction or by using a more reactive metal as a reducing agent. For example, sodium is obtained by electrolysis of molten sodium chloride (Down’s process), magnesium is obtained by electrolysis of molten magnesium chloride, and calcium is obtained by electrolysis of molten calcium chloride (Hall-Héroult process).