You would spend more energy obtaining sodium ions than you would recover in the reaction.
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the sodium ions Na+ are already present in solution in saltwater.
the question is —thanks to the previous poster— where do you get the extra free electron from to attach to the sodium ion Na+ and how do you attach it in situ in solution so that suddenly a sodium metal Na is in the exothermic presence of water H2O
Correct, Na+ is the reaction product. If you dissolve a cup of salt in a quart of water, there will considerable heating, just from the salt going into solution. To recover metallic sodium from that solution requires more energy than recovering it from salt alone.