Sodium (Na, element #11)

What is sodium?
Sodium is the 11th element on the periodic table. It is a highly reactive element that's natural form is a sheet of metal. It is kept in oil or kerosene, because it spontaneously ignites when it is in water. What's weird is, sodium metal also floats on top of water. Sodium flame is always a bright yellow, as shown on the right in a flame test of sodium carbonate.

At room temperature, sodium metal is very durable, so durable that you could easily cut it with a butter knife. Sodium is also a very abundant element. It is found in the sun and in all stars. In fact, it makes up 2.6% of the earth's crust. While sodium on it's own can be found in the places mentioned above, it is also found in various other minerals, most commonly halite.

Why is sodium important?
Sodium is crucial to animals and to us. Animals get most of their nutrition from foods with sodium in it. Sodium also maintains fluid balance throughout the cells and bodies of humans. Without it, we would die. Sodium is also used for food preservation, cooling nuclear reactors, and in sodium vapor lamps. (Sodium vapor lamps are the lights often used as street lights.)

A fireworks show fueled entirely by sodium

Sodium also plays an important role in the creation of fireworks. It is injected into it, and once the fireworks shoot into the sky, it is responsible for the yellow, gold, and orange colored sparks in a firework.