Hierarchy classification:

1. top of the aat hierarchies
2. Materials Facet
3. Materials (hierarchy name)
4. materials (substances)
5. [materials by composition]
6. inorganic material
7. metal
8. [metal by composition or origin]
9. nonferrous metal

Additional parents:

1. top of the aat hierarchies
2. Materials Facet
3. Materials
4. materials
5. materials by form
6. materials by chemical form
7. elements

Anotations

Scope note:

Pure metallic element having symbol Rb and atomic number 37; soft, silvery white, and very reactive, rubidium is found as a trace constituent of various alkali minerals. It is used in photoelectric cells and as a catalyst.