Terminology

Allotropes
Some elements exist in several different structural forms, these are called allotropes.

For more information on Murray Robertson’s image see Uses/Interesting Facts below.

Samarium

Discovery date	1879
Discovered by	P-E. Lecoq de Boisbaudran
Origin of the name	The name is derived from samarskite, the name of the mineral from which it was first isolated.
Allotropes	-

150.36

Fact Box Terminology

Group
Elements appear in columns or ‘groups’ in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.

Period
Elements are laid out into rows or ‘periods’ so that similar chemical behaviour is observed in columns.

Block
Elements are organised into blocks by the orbital type in which the outer electrons are found. These blocks are named for the characteristic spectra they produce: sharp, principal, diffuse, and fundamental.

Atomic Number
The number of protons in the nucleus.

Atomic Radius/non -bonded (Å)
based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties, for more details please refer to the CRC Handbook of Chemistry and Physics.

Electron Configuration
The arrangements of electrons above the last (closed shell) noble gas.

Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.

Melting Point (^oC)
The temperature at which the solid-liquid phase change occurs.

Melting Point (K)
The temperature at which the solid-liquid phase change occurs.

Melting Point (^oF)
The temperature at which the solid-liquid phase change occurs.

Boiling Point (^oC)
The temperature at which the liquid-gas phase change occurs.

Boiling Point (K)
The temperature at which the liquid-gas phase change occurs.

Boiling Point (^oF)
The temperature at which the liquid-gas phase change occurs.

Sublimation
Elements that do not possess a liquid phase at atmospheric pressure (1 atm) are described as going through a sublimation process.

Density (kgm^-3)
Density is the weight of a substance that would fill 1 m³ (at 298 K unless otherwise stated).

Relative Atomic Mass
The mass of an atom relative to that of Carbon-12. This is approximately the sum of the number of protons and neutrons in the nucleus. Where more than one isotope exists the value given is the abundance weighted average.

Key Isotopes (% abundance)
An element must by definition have a fixed number of protons in its nucleus, and as such has a fixed atomic number, however variants of an element can exist with differing numbers of neutrons, and hence a different atomic masses (e.g. ¹²C has 6 protons and 6 neutrons and ¹³C has 6 protons and 7 neutrons).

CAS number
The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems (where several isotopes exist, a value is presented for the most prevalent isotope).

Fact Box

Group	Lanthanides	Melting point	1072 ^oC, 1961.6 ^oF, 1345.15 K
Period	6	Boiling point	1794 ^oC, 3261.2 ^oF, 2067.15 K
Block	f	Density (kg m^-3)	7536
Atomic number	62	Relative atomic mass	150.36
State at room temperature	Solid	Key isotopes	¹⁵²Sm
Electron configuration	[Xe] 4f⁶6s²	CAS number	7440-19-9
ChemSpider ID	22391	ChemSpider is a free chemical structure database

Interesting Facts terminology

Image Explanation

Murray Robertson is the artist behind the images which make up Visual Elements. This is where the artist explains his interpretation of the element and the science behind the picture.

Natural Abundance

Where this element is most commonly found in nature.

Biological Roles

The elements role within the body of humans, animals and plants. Also functionality in medical advancements both today and years ago.

Appearance

The description of the element in its natural form.

Uses / Interesting Facts

Image explanation

The mineral Samarskite was named after Colonel V. E. Samarsky, a Russian mine official. Samarium is also used in lasers.

Appearance

A silvery metal that finds specialised use in glass, ceramics, permanent magnets and electronics.

Uses

Samarium is used to dope calcium fluoride crystals for use in optical lasers. It is also used in infrared absorbing glass and as a neutron absorber in nuclear reactors. In common with other lanthanides, samarium is used in carbon arc lighting for studio lighting and projection.

Biological role

Samarium has no known biological role, and has low toxicity.

Natural abundance

Samarium is found along with other lanthanide metals in several minerals, the principal ones being monazite and bastnaesite. It can be separated from the other components of the mineral by ion exchange and solvent extraction. Recently, electrochemical deposition using lithium citrate as the electrolyte and a mercury electrode has been used to separate samarium from other lanthanides. Samarium can also be produced by reducing the oxide with barium.

Atomic Data Terminology

Atomic radius/non -bonded (Å)
Based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties,for more details please refer to the CRC Handbook of Chemistry and Physics.

Electron affinity (kJ mol^-1)
The energy released when an additional electron is attached to the neutral atom and a negative ion is formed (where several isotopes exist, a value is presented for the most prevalent isotope). *

Electronegativity (Pauling scale)
The degree to which an atom attracts electrons towards itself, expressed on a relative scale as a function bond dissociation energies, E_d in eV. χ_A - χ_B =(eV)-1/2sqrt(E_d(AB)-[E_d(AA)+E_d(BB)]/2), with χ_H set as 2.2 (where several isotopes exist, a value is presented for the most prevalent isotope).

1^st Ionisation energy (kJ mol^-1)
The minimum energy required to remove an electron from a neutral atom in its ground state (where several isotopes exist, a value is presented for the most prevalent isotope).

Covalent radius (Å)
The size of the atom within a covalent bond, given for typical oxidation number and coordination (where several isotopes exist, a value is presented for the most prevalent isotope). ***

Atomic Data

Atomic radius, non-bonded (Å)	2.360	Covalent radius (Å)	1.85
Electron affinity (kJ mol^-1)	Unknown	Electronegativity (Pauling scale)	1.170
Ionisation energies (kJ mol^-1)	1^st 544.524 2^nd 1068.092 3^rd 2257.755 4^th 3994.490 5^th - 6^th - 7^th - 8^th -

Mining/Sourcing Information

Data for this section of the data page has been provided by the British Geological Survey. To review the full report please click here or please look at their website here.

Key for numbers generated

Governance indicators

1 (low) = 0 to 2

2 (medium-low) = 3 to 4

3 (medium) = 5 to 6

4 (medium-high) = 7 to 8

5 (high) = 9

Reserve base distribution

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %

(Where data are unavailable an arbitrary score of 2 was allocated. For example, Be, As, Na, S, In, Cl, Ca and Ge are allocated a score of 2 since reserve base information is unavailable. Reserve base data are also unavailable for coal; however, reserve data for 2008 are available from the Energy Information Administration (EIA).)

Production Concentration

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %

Crustal Abundance

1 (low) = 100 to 1000 ppm

2 (medium-low) =10 to 100 ppm

3 (medium) = 1 to 10 ppm

4 (medium-high) = 0.1 to 1 ppm

5 (high) = 0.1 ppm

(Where data are unavailable an arbitrary score of 2 was allocated. For example, He is allocated a score of 2 since crustal abundance data is unavailable.)

Explanations for terminology

Crustal Abundance (ppm)

The abundance of an element in the Earth's crust in parts-per-million (ppm) i.e. The number of atoms of this element per 1 million atoms of crust.

Sourced

The country with the largest reserve base.

Reserve Base Distribution

This is a measure of the spread of future supplies, recording the percentage of a known resource likely to be available in the intermediate future (reserve base) located in the top three countries.

Production Concentrations

This reports the percentage of an element produced in the top three countries. The higher the value, the larger risk there is to supply.

Total Governance Factor

The World Bank produces a global percentile rank of political stability. The scoring system is given below, and the values for all three production countries were summed.

Relative Supply Risk Index

The Crustal Abundance, Reserve Base Distribution, Production Concentration and Governance Factor scores are summed and then divided by 2, to provide an overall Relative Supply Risk Index.

Supply Risk

Scarcity factor	8.0
Country with largest reserve base	China
Crustal abundance (ppm)	0.3
Leading producer	China
Reserve base distribution (%)	59.30
Production concentration (%)	97.40
Total governance factor(production)	8

Top 3 countries (mined)	1) China 2) USA 3) CIS
Top 3 countries (production)	1) China 2) Russia 3) Brazil

Oxidation states/ Isotopes

Key for Isotopes

Half Life
	y	years
	d	days
	h	hours
	m	minutes
	s	seconds
Mode of decay
	α	alpha particle emission
	β	negative beta (electron) emission
	β+	positron emission
	EC	orbital electron capture
	sf	spontaneous fission
	ββ	double beta emission
	ECEC	double orbital electron capture

Terminology

Common Oxidation states
The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is defined as being the charge that an atom would have if all bonds were ionic. Free atoms have an oxidation state of 0, and the sum of oxidation numbers within a substance must equal the overall charge.

Important Oxidation states
The most common oxidation states of an element in its compounds.

Oxidation States / Isotopes

Common oxidation states	3, 2
Isotopes	Isotope	Atomic mass	Natural abundance (%)	Half life	Mode of decay
	¹⁴⁴Sm	143.912	3.07	-	-
	¹⁴⁷Sm	146.915	14.99	1.06 x 10¹¹ y	a
	¹⁴⁸Sm	147.915	11.24	7 x 10¹⁵ y	a
	¹⁴⁹Sm	148.917	13.82	10¹⁶ y	a
	¹⁵⁰Sm	149.917	7.38	-	-
	¹⁵²Sm	151.92	26.75	-	-
	¹⁵⁴Sm	153.922	22.75	-	-

Pressure and Temperature - Advanced Terminology

Molar Heat Capacity (J mol^-1 K^-1)

Molar heat capacity is the energy required to heat a mole of a substance by 1 K.

Young's modulus (GPa)

Young's modulus is a measure of the stiffness of a substance, that is, it provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain.

Shear modulus (GPa)

The shear modulus of a material is a measure of how difficult it is to deform a material, and is given by the ratio of the shear stress to the shear strain.

Bulk modulus (GPa)

The bulk modulus is a measure of how difficult to compress a substance. Given by the ratio of the pressure on a body to the fractional decrease in volume.

Vapour Pressure (Pa)

Vapour pressure is the measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.

Pressure / Temperature - Advanced

Molar heat capacity
(J mol^-1 K^-1)

29.54

Young's modulus (GPa)

Unknown

Shear modulus (GPa)

Unknown

Bulk modulus (GPa)

Unknown

Vapour pressure

Temperature (K)

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

Pressure (Pa)

8.17
x 10^-8

2.21
x 10^-3

0.94

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History

Elements and Periodic Table History

Samarium was one of the rare earths (aka lanthanoids) which perplexed and puzzled the chemists of the 1800s. Its history began with the discovery of cerium in 1803. This was suspected of harbouring other metals, and in 1839 Carl Mosander claimed to have obtained lanthanum and didymium from it. While he was right about lanthanum, he was wrong about didymium. In 1879, Paul-Émile Lecoq de Boisbaudran extracted didymium from the mineral samarskite. He then made a solution of didymium nitrate and added ammonium hydroxide. He observed that the precipitate which formed came down in two stages. He concentrated his attention on the first precipitate and measured its spectrum which revealed it to be a new element samarium. Samarium itself was eventually to yield other rare-earths: gadolinium in 1886 and europium in 1901.

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Podcasts

Listen to Samarium Podcast

Transcript :

Chemistry in Its Element - Samarium

(Promo)

You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry

(End promo)

Meera Senthilingam

This week, a rare, lustrous element with isotopes that have some unfathomably long half-lives. To tell us more, here's Richard Corfield:

Richard Corfield

Samarium is a rare earth element that - indirectly - has the distinction of being the first naturally occurring chemical element to be named after a living person. Samarium was isolated from the mineral Samarskite which was discovered near the small town of Miass in the southern Ural mountains in 1847. The mineral was named by the German Mineralogist Heinrich Rose after Vasili Evgrafovich Samarsky-Bykhovets, Chief of Staff of the Russian Corps of Mining Engineers between 1845 and 1861 who had given Rose the ore sample to study.

Although Samarium was discovered in 1853 by the Swiss chemist Jean Charles Galissard de Marignac - who first observed its sharp absorption lines in didymium - it was not until 1879 that it was isolated in Paris by the French chemist Paul Emile Lecoq de Boisbaudran using a sample from a newly located ore body in North Carolina.
Samarium is a rare earth metal with a pronounced silver lustre. It oxidizes in air and ignites spontaneously at 150 degrees centigrade. Rare Earth metals are a collection of seventeen chemical elements which include scandium, yttrium and fifteen lanthanoids. The term 'rare earth' is simple a reflection of the fact that these elements were originally isolated from uncommonly occurring oxide-type minerals. Today rare earth metals are increasingly important in the manufacture of high-tech electronic devices.

Samarium's geological origins in Samarskite is entirely in keeping with its importance to the science of geology. Samarium has several isotopes, four of which are stable and several of which are unstable. The half-lives of many of these are very short, on the order of a few seconds but three, ¹⁴⁷Sm, ¹⁴⁸Sm and ¹⁴⁹Sm have extremely long half lives. It is ¹⁴⁷Sm that is the key player in the sub-discipline of geology known as geochronology - the science of assigning absolute dates to minerals. ¹⁴⁷Sm has a staggeringly long half life: 1.06x10¹¹ years or, in real money, 106 billion years. Even by geological standards this gigantic figure is incomprehensible, especially if we remember that the Universe itself is only a little under fourteen billion years old. Thus one kg of ¹⁴⁷Sm will decay to half a kilo of ¹⁴⁷Sm in a period of time that is roughly eight times the duration of the Universe!

Given that the age of the Earth and the other planets of the solar system is only 4.5 billion years, why is this particular element and isotope so useful? Partly it is because the samarium to neodymium decay chain is highly resistant to metamorphosis, the geological process which transforms sedimentary and igneous rocks into other rock types by subjecting them to great heat or pressure or both. This has the effect of redistributing, or fractionating, the original elements. In the case of other geological chronometers, such as the uranium to lead or rubidium to strontium decay series this resets the decay chain clock, rendering them useless. Samarium to neodymium does not suffer from this disadvantage.

Samarium also has a long history in the nuclear industry. Soon after the Second World War the Indianapolis-based chemical giant Eli Lilley developed a fractional crystallisation technique for separating neodymium from ore. The synthesis of samarium and gadolinium was a by-product of the process and since ¹⁴⁹Sm is a strong neutron absorber the product - called 'Lindsay Mix' - was sold as an early form of neutron damper for nuclear control rods. Even today samarium is still used as a neutron absorber in reactor control rods; particularly when mixed with europium and gadolinium forming the so-called samarium-europium-gadolinium (SEG) concentrate.

Samarium has more modest uses as well. These include its use as a component in carbon arc lights in the movie industry, as well as for making magnets that have a high resistance to demagnetisation. Such samarium-based magnets are perfect for both headphones as well as electric guitar pickups. Recently developed samarium/cobalt (SmCo5) magnets have the highest resistance to demagnetisation of any material yet synthesised.
Samarium oxide is also used in optical glass to absorb infrared radiation as well as to dope calcium fluoride crystals in optical lasers.

Samarium, like other rare earths is becoming progressively more valuable in a world whose dependence on high-technology is snow-balling. Recent reports have highlighted concerns that the Chinese are hoarding their native reserves of the rare earths to feed their electronic industries. This will certainly have the effect of hiking the price of samarium and the other rare earth elements so it may be time to consider buying share options. Not bad for an element first discovered in the mountains of tsarist Russia and which has - until now - been mostly noted for its arcane role in dating exotic rocks.

Meera Senthilingham

So get those samarium shares in ASAP. That was science writer Richard Corfield with the geological and technological uses of the element samarium. Now next week, we stick with the lanthanides and hear about an element that likes to play hard to get.

Simon Cotton

At that time, scientists were using improved techniques such as fractional crystallisation to obtain the individual lanthanides from mixtures. In 1886, Lecoq was the first person to identify dysprosium by separating its oxide from holmium oxide. It took him over 30 goes to do this, so he named the element accordingly, from the Greek word, dysprositos, meaning "hard to get at".

Meera Senthilingham

And Simon Cotton will be sharing some of the chemistry, properties and applications of dysprosium in next week's Chemistry in its Element. Until then, I'm Meera Senthilingham and thank you for listening

(Promo)

Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists dot com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld dot org forward slash elements.

(End promo)

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References

Images: Visual Elements © Murray Robertson 2011
Mining and Sourcing data: British Geological Survey – natural environment research council.
Text: John Emsley Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, 2nd Edition, 2011.
Additional information for platinum, gold, neodymium and dysprosium obtained from Material Value Consultancy Ltd www.matvalue.com
Data: CRC Handbook of Chemistry and Physics, CRC Press, 92nd Edition, 2011.
G. W. C. Kaye and T. H. Laby Tables of Physical and Chemical Constants, Longman, 16th Edition, 1995.
Members of the RSC can access these books through our library.

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