27 Transition metal
45 Transition metal
77 Transition metal
109 unknown chemical properties
Group 9 is a group (column) of chemical elements in the periodic table. Members are cobalt (Co), rhodium (Rh), iridium (Ir) and meitnerium (Mt).[page needed] These are all transition metals in the d-block.
Like other groups, the members of this family show patterns in electron configuration, especially in the outermost shells, resulting in trends in chemical behavior; however, rhodium deviates from the pattern.
In the older group naming systems, this group was combined with group 8 (iron, ruthenium, osmium, and hassium) and group 10 (nickel, palladium, platinum, and darmstadtium) and called group "VIIIB" in the Chemical Abstracts Service (CAS) "U.S. system", or "VIII" in the old IUPAC (pre-1990) "European system" (and in Mendeleev's original table).
|Z||Element||No. of electrons
|27||cobalt||2, 8, 15, 2||1768 K
|45||rhodium||2, 8, 18, 16, 1||2237 K
|1803||W. H. Wollaston|
|77||iridium||2, 8, 18, 32, 15, 2||2719 K
|109||meitnerium||2, 8, 18, 32, 32, 15, 2[*]||--||--||1982||P. Armbruster and|
The first three elements are hard silvery-white metals:
Cobalt is a metallic element that can be used to turn glass a deep blue color.
Rhodium can be used in jewelry as a shiny metal.
Iridium is mainly used as a hardening agent for platinum alloys.
All known isotopes of meitnerium are radioactive with short half-lives. Only minute quantities have been synthesized in laboratories. It has not been isolated in pure form, and its physical and chemical properties have not been determined yet.