Group 9 element

Group 9, by modern IUPAC numbering,[1] is a group (column) of chemical elements in the periodic table. Members of Group 9 include cobalt (Co), rhodium (Rh), iridium (Ir) and meitnerium (Mt).[2] These are all transition metals in the d-block, considered to be some of the most rare of which.[3]

Group 9 in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
group 8    group 10
IUPAC group number9
Name by elementcobalt group
CAS group number
(US, pattern A-B-A)
part of VIIIB
old IUPAC number
(Europe, pattern A-B)
part of VIII

Cobalt (Co)
27 Transition metal
Rhodium (Rh)
45 Transition metal
Iridium (Ir)
77 Transition metal
7 Meitnerium (Mt)
109 unknown chemical properties


primordial element
synthetic element
Atomic number color:

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.

"Group 9" is the modern standard designation for this group, adopted by the IUPAC in 1990.[2]

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).


ZElementNo. of electrons
per shell
M.P.B.P.Year of
27cobalt2, 8, 15, 21768 K
1495 °C
3200 K
2927 °C
~1735Georg Brandt
45rhodium2, 8, 18, 16, 12237 K
1964 °C
3968 K
3695 °C
1803W. H. Wollaston
77iridium2, 8, 18, 32, 15, 22719 K
2446 °C
4403 K
4130 °C
1803S. Tennant
109meitnerium2, 8, 18, 32, 32, 15, 2[*]1982P. Armbruster and
G. Münzenberg

[*] Predicted.

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.

See also


  1. Fluck, E. (1988). "New Notations in the Periodic Table" (PDF). Pure Appl. Chem. 60 (3): 431–436. doi:10.1351/pac198860030431. S2CID 96704008. Retrieved 24 March 2012.
  2. Leigh, G. J. Nomenclature of Inorganic Chemistry: Recommendations 1990. Blackwell Science, 1990. ISBN 0-632-02494-1.
  3. "Group 9: Transition Metals". Chemistry LibreTexts. 2020-08-15. Retrieved 2022-03-24.{{cite web}}: CS1 maint: url-status (link)
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.