Sodium is considered a metal, as it is part of the alkali metals group. The other members of this group include lithium, cesium, rubidium, potassium and francium.
Pure sodium is a soft, silvery metal that is incredibly reactive with both air and water. It is so highly reactive that pure sodium cannot exist on its own in nature. Nonetheless, there are many sodium compounds that are common in nature, such as sodium chloride, also known as table salt. In fact, sodium is the sixth most common element on the planet and makes up nearly 3 percent of the Earth's crust.