The highly reactive oxygen combines with hydrogen and carbon monoxide on the fuel side to make water and CO 2.

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Clusters of zinc atoms then mix with a reactive gas, usually oxygen, and cool to a solid.

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Oxygen, for instance, is a reactive gas that ought to end up quickly bound within rocks.

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The problem is that calcium, magnesium and lithium are a bit fussy and chemically quite reactive and will oxidize or stop working if they are exposed to oxygen and moisture.

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