Platinum is a dense, silvery-white metal utilized for centuries. Its name originates from the Spanish word platina, meaning “little silver.” Its exceptional resistance to corrosion and tarnish has cemented its status as a precious commodity.
Platinum’s Identity as a Chemical Element
Platinum is formally designated on the periodic table as a transition metal with the chemical symbol Pt. It possesses an atomic number of 78 and a standard atomic weight of approximately 195.084. As a transition metal, it resides in Group 10 and Period 6 of the periodic table.
The element is considered one of the rarest metals in the Earth’s crust, found at a very low concentration of about 5 micrograms per kilogram. Platinum typically occurs in its uncombined, or native, state, often alloyed naturally with other similar metals. Its scarcity contributes significantly to its high value compared to more common metals.
Classification as a Platinum Group and Noble Metal
Platinum belongs to the Platinum Group Metals (PGMs) and the Noble Metals. The PGMs are a family of six elements—platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir), and osmium (Os)—that share similar physical and chemical characteristics and are usually found together in the same mineral deposits.
Platinum’s membership in the PGMs is based on shared properties such as high density, excellent catalytic activity, and high melting points. The metal is also classified as a Noble Metal, a designation that speaks directly to its chemical stability. Noble metals are those that resist chemical action, oxidation, and corrosion, even at high temperatures.
This extreme chemical inertness means platinum does not readily react with oxygen to form oxides, nor does it tarnish in air. Its stability is so high that it is immune to attack by most individual acids. However, it can be dissolved by a mixture of nitric and hydrochloric acids known as aqua regia.
Physical Properties and Primary Applications
The metal is exceptionally dense, measuring 21.45 grams per cubic centimeter, which is nearly twice the density of lead. This high density contributes to its substantial feel, particularly in jewelry. It also features a remarkably high melting point of 1,768 degrees Celsius.
Despite its high melting point, platinum is both highly malleable and ductile, meaning it can be hammered into thin sheets or drawn into fine wires. These characteristics make it a preferred material for fine jewelry, where its resistance to tarnish ensures a lasting, lustrous, silvery-white appearance. The metal’s durability and non-reactivity also make it ideal for use in laboratory equipment, such as crucibles and electrodes.
One of the most important industrial uses for platinum is in catalysis. Platinum is a major component in automotive catalytic converters, where it facilitates the conversion of harmful exhaust emissions, such as carbon monoxide and nitrogen oxides, into less harmful substances like carbon dioxide and water vapor. Furthermore, its inertness and biocompatibility—meaning it does not react negatively with biological tissue—make platinum compounds, like cisplatin, integral to certain chemotherapy drugs for cancer treatment and for use in medical implants like pacemakers.