This element is classified as a lanthanide and it is the most abundant of the rare-earth elements of the earth’s crust. It is the most reactive of the rare-earth metals and is used as a catalyst to refine petroleum.
This element is the lightest alkali metal and it is very reactive. This metal is used for the production of dry cells and storage batteries (for cell phones, car batteries, etc.). The carbonate of this metal is used for the treatment of some mental decease.
This element is classified as an actinide and it is solid at room temperature. It is a synthetic transuranic element and can be produced in kilogram quantities. It is used in smoke detectors and as a portable source of gamma rays.