Sodium is a metal in its pure form, but not like what you’d normally think of as a metal. It is extremely soft – so soft that you can scrape pieces off with a plastic spoon. A freshly scraped piece of sodium has the shiny silvery color that we tend to associate with metals, but sodium reacts so quickly with the moisture in the air that it soon takes on a dull grey-white coating. Because sodium does react so readily with water, it is generally stored in oil – an inert environment.
Sodium is so very reactive because of its electron configuration. Like all Group I metals (lithium, sodium, potassium, rubidium, cesium, francium), sodium has only one electron in its outermost shell. The ten inner electrons (sodium is element number 11, so there are 11 protons and 11 electrons) shield that outermost electron from most of the attractive force of the nucleus, so that very little energy is required to strip it away (a low ionization energy). Because sodium can lose its electron so easily, it is known as a strong reducer (reducers give electrons to other chemicals). Sodium will react with any oxidizer it comes into contact with. (An oxidizer takes electrons. Oxygen is a common oxidizer, hence the name.)
Because sodium reacts so readily with other elements and compounds, it is not found in nature. It does exist in a number of everyday compounds, including:
sodium chloride – table salt
sodium bicarbonate – baking soda
sodium hydroxide – used to make soap, clean drains, and a good strong base in the lab
sodium acetate – in the aftermath of vinegar & baking soda volcanoes
sodium benzoate – a commercial food preservative
sodium fluoride – often in city water to promote healthy teeth
Sodium is found in many other compounds as well, most of which are irrelevant unless you are working in a chemistry lab.
Pure sodium has limited uses because it is so very reactive. Most people will only see it in class demonstrations, where the teacher tosses a bit of it into water, where it quickly reacts to produce hydrogen, and depending on the size of the sodium piece, either dances on the surface of the water (buoyed up by hydrogen bubbles), jumps up from the water (propelled by larger bubbles or even small explosions from the ignition of hydrogen), or explodes (because the generation of hydrogen and heat are too rapid in a larger piece). There is actually a great video of this out there – search for “The Great Sodium Disaster” to see a brick of sodium thrown into a reservoir.
Constructive uses of sodium do exist. Because sodium is such a strong reducer, it can be used in the synthesis of other compounds, generally as an intermediate. Sodium is comparatively cheap for this purpose, and readily available. (It is easily made by reducing the sodium ions in salt.)
Sodium can also be used in the construction of a battery. Most people are now familiar with lithium ion batteries. With sodium in the same chemical family as lithium, it should be no surprise that it too can be used. Read up on the sodium-sulfur (NaS) cell if you’re curious.
