Name one metal and one non-metal which are obtained on a large scale from seawater

The metal that is obtained on a large scale from seawater is Magnesium. Seawater contains a variety of salts, and magnesium can be obtained through the evaporation of seawater.

The non-metal that is obtained on a large scale from seawater is Chlorine. Chlorine is produced from seawater by electrolysis. The process also produces hydrogen, and sodium hydroxide which can be used to neutralize the resulting hydrochloric acid.