Symbol

Os

Atomic Number

76

Atomic Mass

190.2

Family

Group 8 (Viiib) Transition Metal Platinum Group Pronunciation

OZ-mee-um

Overview

Osmium is an element in Group 8 (VIIIB) of the periodic table. The periodic table is a chart showing how chemical elements are related to one another. Osmium is also a member of the platinum family. This family consists of five other elements: ruthenium, rhodium, palladium, indium, and platinum. These elements often occur together in the Earth's crust. They also have similar physical and chemical properties, and are used in alloys.

Osmium was discovered in 1804 by English chemist Smithson Tennant (1761-1815). Tennant found the new element in an ore of platinum.

Osmium is a very rare element and has few commercial uses. Osmium tetroxide (OsO₄), is more widely used, however, because it is so active.

Discovery and Naming

Platinum metal (atomic number 78) was known to chemists as early as 1741. Over the next 60 years...