Which elements are lanthanides

With the exception of promethium, Pm, which does form a stable isotope, even the least abundant thulium, Tm, and lutetium, Lu, are as abundant as iodine. Because lanthanoids have very similar properties and are difficult to separate from one another, they were not useful for basic research and application, and hence they were regarded as rare elements.

Its name is derived from the Greek words neos and didymos , meaning "new twin. It is found in the Earth's crust at a concentration of 38 ppm, making it the 27th most abundant element. It is found chiefly in the ores monazite and bastnasaite see introduction. Neodymium oxidizes easily in both air and water.

Neodymium is used to strengthen alloys of magnesium. It is also alloyed with iron and boron to make NIB magnets, which are extremely strong permanent magnets. These are sometimes referred to as "rare earth magnets" or "neodymium magnets. Promethium is an unstable, radioactive element which is only found on Earth in minute quantities in uranium ores.

Its existence was suspected for some time, because there was no known element with 61 protons in its nucleus, but there were no universally agreed-upon reports of its discovery until , when it was isolated by researchers who were separating and purifying uranium fission products at the Oak Ridge National Laboratory in Oak Ridge, Tennessee. It is named for the Greek god Prometheus, who stole fire from the gods and gave it to mankind, and was punished by being chained to a rock and having his liver eaten by a eagle every day.

The most stable isotope of the element, promethium, has a half-life of There are a number of other isotopes as well, but the majority of them have half-lives that are less than 30 seconds. Promethium is found in trace amounts in uranium ores, but because it is so unstable, it never accumulates above the concentration of about a picogram 10 g per ton of ore. The spectral lines of promethium have also been observed in some stars. Promethium emits beta particles, and in the presence of elements of higher atomic weight can stimulate the release of X-rays.

It can be produced artificially by the bombardment of neodymium with neutrons to form neodymium, which decays into promethium and a beta particle. Because promethium is so unstable, it has few practical applications, but it is used as a beta-particle emitter for thickness gauges used for measuring the thickness of sheets of steel, in some luminous blue and green paints, and in miniature batteries used in guided missiles and pacemakers. Samarium is a silvery metal. It is named for the mineral samarskite, from which it was first obtained.

It is present in the Earth's crust at a concentration of 8 ppm, making it the 40th most abundant element. Samarium is used in alloys with cobalt to make strong permanent magnets which have a high resistance to demagnetization.

It is also used in carbon-arc lights used in motion picture studios, as a neutron absorber in nuclear reactors, and in optical glass to absorb infrared light. Europium is a soft, silvery-white metal. It is named for the continent of Europe. It is found in the Earth's crust at a concentration of 2 ppm, making it the 50th most abundant element.

It is obtained from the ore monazite see introduction , which contains up to 2. Lanthanides Properties and Elements. Transition Metals: List and Properties. Properties and Reactions of the Actinide Series of Elements. Metallic Character: Properties and Trends. Element Families of the Periodic Table. Periodic Table Definition in Chemistry. Metals Versus Nonmetals - Comparing Properties. Your Privacy Rights. To change or withdraw your consent choices for ThoughtCo.

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Develop and improve products. List of Partners vendors. Share Flipboard Email. Anne Marie Helmenstine, Ph. Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels. Facebook Facebook Twitter Twitter. Updated December 12, Featured Video.