Group 9 element

Some metals are part of a special group.

One metal is called cobalt. It can turn glass a deep blue color. People have used it for a long time.

Other metals in this group are very rare. Rhodium and iridium are very expensive. They cost more than gold!

These metals are hard and shiny. Rhodium is very bright. Iridium does not rust or break down easily.

One metal, called meitnerium, is made in a lab. It is not found in nature.

Cobalt is also good for living things. It helps make a vitamin for animals.

Some metals belong to a special family called Group 9. This group has four members. They are cobalt, rhodium, iridium, and meitnerium. These metals are often very rare. In fact, rhodium and iridium cost more than gold by weight.

Cobalt is a very useful metal. People have used it for a long time. It can turn glass and ceramics a deep blue color. Cobalt is also used in batteries. It helps make strong alloys. One special part of cobalt helps living things. It is part of vitamin B. Bacteria in the stomachs of some animals make this vitamin. This helps the animals stay healthy.

Other metals in this group are very tough. Rhodium is a shiny, bright metal. It is often used in jewelry. Iridium is very hard to break down. It is the most corrosion-resistant metal known. This means it does not rust or get damaged by acids.

Meitnerium is different from the others. It is a synthetic element. This means it is made by people in a lab. It is not found in nature. Scientists first made it in 1982.

Some metals belong to a special family called Group 9. This group is a column in the periodic table. It includes cobalt, rhodium, iridium, and meitnerium. These metals are among the rarest transition metals. As of 2025, rhodium and iridium are very expensive. They cost more per weight than gold.

Each member shows similar patterns in their electrons. This leads to similar chemical behaviors. However, rhodium is a bit different from the others. The name Group 9 was chosen by the IUPAC in 1990. Before this, they used older naming systems like group VIIIB.

Cobalt is a metal that has been used for many centuries. People use cobalt compounds to make glass and ceramics a deep blue. Scientists found cobalt in Egyptian sculpture and Persian jewelry. It was even found in the ruins of Pompeii from 79 AD. Cobalt is also used in lithium-ion batteries today. It helps make strong alloys and can clean sulfur from crude oil. This helps prevent acid rain.

Cobalt is also very important for living things. It is a key part of vitamin B, or cobalamin. Bacteria in the stomachs of grazing animals make this vitamin. Without it, these animals would not stay healthy.

Finding these metals took a long time. A Swedish chemist named Georg Brandt discovered cobalt around 1735. He showed it was a new metal, not bismuth. Cobalt was the first metal discovered since pre-historic times. In 1803, William Hyde Wollaston discovered rhodium. He used platinum ore from South America to find it. He dissolved the ore in a liquid called aqua regia. Then, he used sodium chloride to make the rhodium appear.

This was a very careful way to separate the metal.

Iridium was also found in 1803 by Smithson Tennant. He was studying a dark residue left after dissolving platinum. He found that this residue contained two new metals. One was iridium and the other was osmium. He named iridium after Iris, the Greek goddess of the rainbow. He chose this name because the metal's salts have many colors.

Iridium is the most corrosion-resistant metal we know. This means it is not attacked by acids. It is also used to make platinum alloys much harder.

Meitnerium is different because it is a synthetic element. This means it is made by people in a laboratory. It is not found naturally in the Earth. A German team first made it on August 29, 1982. The team was led by Peter Armbruster and Gottfried Münzenberg. They used a machine to hit bismuth with iron nuclei. They found only one single atom of meitnerium-266.

All known versions of meitnerium are radioactive. Because they are radioactive, they do not last very long.

Group 9 is a specific column of chemical elements in the d-block of the periodic table. This family includes cobalt, rhodium, iridium, and the synthetic element meitnerium. These elements are among the rarest of the transition metals. As of 2025, rhodium and iridium are the only non-radioactive metals with higher prices per weight than gold. Members of this group share patterns in their electron configuration. This refers to how electrons are arranged in their outermost shells. These patterns cause the elements to show similar trends in chemical behavior. However, rhodium is a notable exception that deviates from this group pattern.

The history of naming this group has changed over time. The modern designation "Group 9" was adopted by the IUPAC in 1990. Before this change, different systems used different names. In the Chemical Abstracts Service "U.S. system," the group was called VIIIB. It was combined with group 8 and group 10. In the older IUPAC "European system," it was simply called VIII. This was also the name used in Mendeleev's original periodic table. These changes helped create a single, modern standard for scientists to follow.

Cobalt is a hard, silvery-white metal with many uses. For centuries, people have used cobalt compounds to create a rich blue color. This color is found in glass, glazes, ceramics, inks, paints, and varnishes. Specifically, cobalt silicate and cobalt(II) aluminate provide this deep blue shade. Cobalt is also vital for modern technology. It is used in lithium-ion batteries and in making high-strength, wear-resistant alloys. In the petroleum industry, cobalt acts as a catalyst. It helps refine crude oil by removing sulfur. Removing sulfur is important because burning it causes polluting acid rain.

Cobalt also plays a critical biological role that other group 9 elements do not. It is a key part of cobalamin, which is also known as vitamin B. This is the primary way cobalt exists as an ultratrace element in living things. In the stomachs of ruminant animals, bacteria convert cobalt salts into vitamin B. These animals cannot produce the vitamin themselves. Therefore, a minimal amount of cobalt in soil is necessary for the health of grazing animals. In humans, vitamin B12 helps with important chemical tasks. For example, methylmalonyl coenzyme A mutase helps extract energy from fats and proteins.

The discovery of cobalt was a major event in science. A Swedish chemist named Georg Brandt discovered it around 1735. He proved it was a new element and not bismuth. Brandt called it a "semi-metal." This was the first metal discovered since the pre-historical period. All other known metals, like gold or iron, had no recorded discoverers. Cobalt has been found in many ancient places. It appeared in Egyptian sculpture and Persian jewelry from the third millennium BC. It was even found in the ruins of Pompeii, which was destroyed in 79 AD.

Rhodium and iridium were discovered in 1803 through very careful chemical processes. William Hyde Wollaston discovered rhodium using platinum ore from South America. He dissolved the ore in aqua regia, which is a mixture of nitric and hydrochloric acids. He then used sodium chloride to precipitate the rhodium. He later reacted a rose-red precipitate with zinc to release the free metal. Around the same time, Smithson Tennant analyzed a dark, insoluble residue left from dissolving platinum. He identified two new elements in that residue: iridium and osmium. He named iridium after Iris, the Greek goddess of the rainbow. He chose this because the metal's salts are strongly colored.

Iridium is famous for being the most corrosion-resistant metal known. This means it is not attacked by acids, even aqua regia. Because of this strength, it is often used as a hardening agent for platinum alloys. Rhodium is also very durable and has high reflectance. It is used in jewelry to provide a shiny finish. Unlike many other metals, rhodium does not normally form an oxide when heated. It is also insoluble in nitric acid. These properties make both metals highly valuable and useful in specialized science and industry.

Meitnerium is the most different member of the group because it is synthetic. This means it is made by humans in a lab rather than found in nature. A German research team led by Peter Armbruster and Gottfried Münzenberg first synthesized it on August 29, 1982. They worked at the Institute for Heavy Ion Research in Darmstadt. The team bombarded a target of bismuth-209 with accelerated iron-58 nuclei. This process detected a single atom of the isotope meitnerium-266. This discovery was confirmed three years later in the Soviet Union. All known isotopes of meitnerium are radioactive and have short half-lives. Because of this, it has not been isolated in pure form.