Alkali metals are highly reactive, explosive metals found in Group 1 of the periodic table. This group of elements includes sodium, potassium, rubidium, lithium, cesium and francium. While they all occur in nature, they occur in their pure forms only as salts. Each alkali metal has its own list of interesting properties.
Sodium is the most abundant of the alkali metals, and it produces a golden yellow flame. Humans and animals cannot live without sodium chloride as it plays an important role in fluid and electrolyte balance. It is also used in colder months to control ice on roadways. Lithium, named after the Greek word "lithos," which means "stone," is the least dense of all the alkali metals. It is commonly used in rechargeable batteries, cell phones, computers and camcorders. Potassium is also abundant on Earth, and it produces a lavender flame when heated. Potassium is an essential nutrient for plant growth and is therefore used to produce fertilizers.
Rubidium is named after the Latin word for "red," and it produces a thick brick red flame. It is so highly reactive to water and air that it must be stored in oil for safety reasons. Cesium, sometimes spelled "caesium," it is the material most often used to make atomic clocks. Cesium clocks are considered the most precise and accurate timekeeping devices. Francium was discovered in 1939, and it is extremely radioactive. It is the heaviest of the alkali metals and has the lowest boiling point. It is also the most reactive of the alkali metals.