Sodium (Na) is one of the necessary, essential electrolytes and should be balanced with magnesium and potassium.
Also, a rarely mentioned reason for table salt intake in the U.S. is that it's one of the few food additives that is [optionally] supplemented with iodine (check the label for "contains iodine" or "provides iodine" wording), which is a necessary nutrient, usually in the form of potassium iodide (KI).
Not all commercial table salt is iodized, so it's important to read the label. Some, but not all, sea salts have the traces of iodine and other minerals.
A rich source of iodine is seaweed, but few people in the U.S. consume it, though it's popular among Asians, particularly of Japanese ancestry.
Info on halogens, history and reasons for higher rates of iodine deficiency (take some suggestions with a pinch of salt) :
Iodine is vital for good health - Dr. James Howenstine, 2005 November 05
How important is Iodine for our health? - 2010 September 12
Thanks for the links.