Osmium Density and Melting Point

Osmium, a metallic chemical element is one of the rarest found elements on Earth and it mainly exists in alloys. The name osmium has been derived from the Greek word, osme, meaning the smell or odor. It was discovered in 1803, by an English chemist, Smithson Tennant, who found the presence of this chemical element in residue of crude platinum, after the platinum was dissolved in aqua regia mixture. Being a part of the precious, platinum group members (PGMs) osmium has unique features.

An Overview of Osmium Density and Melting Point

Amongst various features of Osmium, its density and melting point are noteworthy. One of the most popular facts about osmium is that, as per various studies and researches, osmium density is the highest amongst various known natural element to mankind and it competes closer to the other platinum group member, iridium, in density. In the recent years, there has been confusion as to which is the densest metal known, as the density values of osmium and iridium are quite close to each other. However, after deep study and research, by using lattice parameters, the density of osmium has been found to be slightly higher than that of iridium and hence, at 20°C,osmium is the densest element. The density of the 10 densest metals have been presented below in a tabular form.

Element	Density (g/cm3)
Osmium	22.6
Iridium	22.4
Platinum	21.45
Rhenium	21.04
Uranium	20.2
Americium	19.84
Tungsten	19.35
Gold	19.32
Neptunium	18.95
Tantalum	16.65

Reason Behind Osmium Being the Densest Element: Lanthanide Contraction
To understand the term lanthanide contraction, it is important to go through the periodic table with atomic mass. In the periodic table, as you will find, the elements starting from cerium, 58, to Lutetium, 71 are known as Lanthinides and lanthanide contraction is nothing but a decrease in the ionic radii of lanthanide elements from cerium 58 to Lutetium, 71. Due to increase in effective nuclear charge while going from left to right in the periodic table, there is a reduction in the atomic size. Since osmium has a atomic number 76 and lies in the same group 6, the effects of lanthanide contractions are seen on its density. Atomic radii of platinum group members, especially osmium is almost same as the fifth group elements but the atomic masses are almost twice the fifth group elements. Hence, owing to lanthanide contraction, osmium density is very high.

Osmium Melting Point
The melting point of osmium is 3045°C, which is the highest amongst the platinum group members and fourth highest amongst all elements. Presented below is a tabulated data about the chemical elements with highest MP.

Element	Melting Point (°C)
Ruthenium	2250
Boron	2300
Iridium	2410
Niobium	2468
Molybdenum	2617
Tantalum	2996
Osmium	3045
Rhenium	3180
Tungsten	3410
Carbon	3500

Osmium, the lustrous, silvery metal, is an important element in the PMGs. As stated earlier, the high density of osmium and its MP are considered to be the reason behind various chemical properties of osmium. With the atomic number 76, and electronic configuration, [Xe]4f¹⁴5d⁶6s², osmium finds usage in a variety of alloys in the industry. It is also used as a catalyst in the chemical industry. One of the osmium facts is that it is highly toxic and disastrous.

PS: The data about melting point and density are approximate and not exact.