It is one part of salt.

It's a soft silvery metal that explodes on contact with water!

It's also a component of common salt.

On 4 Jun 2005 06:01:07 -0700, amsdcj@hotmail.com wrote in
<news:1117889398.491503.263290@g47g2000cwa.googlegroups.com> on
sci.med.nutrition :

http://www.answers.com/sodium

"...Among the most important compounds are chloride (common salt, NaCl),
bicarbonate (baking soda, NaHCO3), carbonate (soda ash, or washing soda,
Na2CO3), hydroxide (caustic soda, or lye, NaOH), nitrate (Chile saltpeter,
NaNO3), thiosulfate (hypo, Na2S2O3·5H2O), phosphates, and borax
(Na2B4O7·10H2O). Sodium hydroxide is used wherever a cheap alkali is
needed, for example, in making soap. Substances containing sodium impart a
characteristic yellow color to a flame. Because of its activity sodium is
not found uncombined in nature. It occurs abundantly and widely distributed
in its compounds, which are present in rocks and soil, in the oceans, in
salt lakes, in mineral waters, and in deposits in various parts of the
world. Sodium compounds are found in the tissues of plants and animals.
Sodium is an essential element in the diet, but some people must limit the
amount of sodium in their food for medical reasons..."
[...]
"Sodium (English, soda) has long been recognized in compounds, but was not
isolated until 1807 by Sir Humphry Davy through the electrolysis of caustic
soda. In medieval Europe a compound of sodium with the Latin name of
sodanum was used as a headache remedy. Sodium's symbol, Na, comes for the
neo-Latin name for a common sodium compound named natrium, which comes from
the Greek nítron, a kind of natural salt..."

===

http://www.health.gov/dietaryguidelines/dga2005/document/html/chapter8.htm
[Dietary Guide lines for Americans, 2005 - Sodium and Potassium]

"On average, the higher an individual's salt (sodium chloride)
intake, the higher an individual's blood pressure. Nearly
all Americans consume substantially more salt than they
need. Decreasing salt intake is advisable to reduce the
risk of elevated blood pressure. Keeping blood pressure in
the normal range reduces an individual's risk of coronary
heart disease, stroke, congestive heart failure, and kidney
disease. Many American adults will develop hypertension
(high blood pressure) during their lifetime. Lifestyle
changes can prevent or delay the onset of high blood
pressure and can lower elevated blood pressure. These
changes include reducing salt intake, increasing potassium
intake, losing excess body weight, increasing physical
activity, and eating an overall healthful diet."

"Salt is sodium chloride. Food labels list sodium rather than
salt content. When reading a Nutrition Facts Panel on a
food product, look for the sodium content. Foods that are
low in sodium (less than 140 mg or 5 percent of the Daily
Value [DV]) are low in salt."

"Common sources of sodium found in the food supply are
provided in figure 4. On average, the natural salt content
of food accounts for only about 10 percent of total intake,
while discretionary salt use (i.e., salt added at the table
or while cooking) provides another 5 to 10 percent of total
intake. Approximately 75 percent is derived from salt
added by manufacturers. In addition, foods served by food
establishments may be high in sodium. It is important to
read the food label and determine the sodium content of
food, which can vary by several hundreds of milligrams
in similar foods. For example, the sodium content in
regular tomato soup may be 700 mg per cup in one brand
and 1,100 mg per cup in another brand. Reading labels,
comparing sodium contents of foods, and purchasing the
lower sodium brand may be one strategy to lower total
sodium intake (see table 15 for examples of these foods).
An individual's preference for salt is not fixed. After
consuming foods lower in salt for a period of time, taste
for salt tends to decrease. Use of other flavorings
may satisfy an individual's taste. While salt substitutes
containing potassium chloride may be useful for some
individuals, they can be harmful to people with certain
medical conditions. These individuals should consult
a healthcare provider before trying salt substitutes."

"Discretionary salt use is fairly stable, even when foods
offered are lower in sodium than typical foods consumed.
When consumers are offered a lower sodium product, they
typically do not add table salt to compensate for the lower
sodium content, even when available. Therefore, any
program for reducing the salt consumption of a population
should concentrate primarily on reducing the salt used
during food processing and on changes in food selection
(e.g., more fresh, less-processed items, less sodium-dense
foods) and preparation..."

[..cut..]

Sodium is a metal that is an essential mineral to the human body.

a chemical element.