(Na, Na+, latin Natrium)
Although sodium is metal it is not found in nature in its free form, but just in compounds or ionic form. It was first isolated by Humphry Davy in 1807.
Sodium ions are needed in small amounts in plants and much more in humans duo to its important role.
Salt, which is the main source of sodium, had a very important role in people's lives in past, so it was used for payment of salaries. Thus, for example, the Roman soldiers sometimes in addition to other income received and a lump of salt.