Group 9 element
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.
|Group 9 in the periodic table|
27 Transition metal
45 Transition metal
77 Transition metal
109 unknown chemical properties
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. 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.