What is Sodium? - Definition, Facts, Properties & Uses

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  • 0:05 Definition of Sodium
  • 0:40 Properties
  • 2:03 History
  • 2:55 Uses
  • 3:59 Lesson Summary
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Lesson Transcript
Instructor: Elizabeth (Nikki) Wyman

Nikki has a master's degree in teaching chemistry and has taught high school chemistry, biology and astronomy.

Sodium is everywhere. It's in your sweat, it's in your food, and it's even in the ocean. But, don't be afraid of this common and useful element. In this lesson, learn about the definition of sodium, its properties and uses and even some cool facts.

Definition of Sodium

Not to alarm you, but sodium really is everywhere, and we hear about it frequently in our daily lives. It is a nutrient we need to properly function. It is also a preservative, a flavor enhancer, and even part of many cleaning solutions. Sodium is found in rocks and in the ocean, and it's what gives many old street lamps their yellow-orange glow.

Believe it or not, sodium is a metal. To be more specific it is an alkali earth metal. It is shown in column 1 (1A) of the periodic table with atomic number 11. The symbol for sodium is Na, which comes from the Latin name for sodium, natrium.


If you ever get a chance to see pure sodium metal, you'll notice that it is silvery and lustrous. Pure sodium metal is very soft and can be cut with a dull knife. It can conduct heat and electricity; however it is rarely used for this purpose. The melting point of sodium metal is 208.0 degrees Fahrenheit, and it boils at 1621.3 degrees Fahrenheit. It is not a dense metal and will float on water. The most common form of sodium has an atomic weight of 23 amu (atomic mass units). However, the average atomic weight of sodium is 22.99 amu.

Like all of the alkali earth metals, sodium in its pure, metallic form, has one electron in its outermost shell that is very easily removed. Because of this, pure sodium is incredibly reactive. It will readily react with water and even oxygen in the air, producing heat and flammable hydrogen gas. In fact, simply putting a chunk of sodium metal in water makes fire! Pure sodium is often kept in mineral oil to keep it from reacting with its surroundings.

Because pure sodium is so reactive, it's seldom found in its pure form. Sodium occurs most frequently as a cation, which is a positively charged particle. Sodium loses its one outermost electron to become a +1 cation. The sodium cation is represented as Na+.


In 1807, Humphrey Davy discovered sodium after he passed an electric current through the compound sodium hydroxide, separating sodium from hydroxide. A similar process is still used today to make pure sodium metal. Sodium metal doesn't have as many commercial uses as sodium in its cation form. Every year, tons of sodium cation containing compounds are produced.

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