Samarium (Sm)

Samarium is a chemical element with the atomic number 62 in the periodic table. With an abundance of 6 parts per million, it’s the 40th most abundant chemical element in Earth’s crust. 

Being a member of the lanthanides family of periodic table elements, this rare-earth element is a divalent substance that’s widely used in the electronic and metal industries. Also, many of samarium isotopes are used in medicine as a part of cancer therapy for their ability to destroy the cancer cells. 

Chemical and Physical Properties of Samarium

Property	Value
Symbol	Sm
Atomic number	62
Atomic weight (mass)	150.35 g.mol-1
Group (number)	Lanthanides
Period	6 (f-block)
Color	Silvery color with pronounced lustre
Physical state	Solid at room temperature
Half-life	From 0.5# seconds to 7×1015 years
Electronegativity according to Pauling	1.2
Density	6.9 g.cm-3 at 20°C
Melting point	1072°C, 1962°F, 1345 K
Boiling point	1794°C, 3261°F, 2067 K
Van der Waals radius	N/A
Ionic radius	N/A
Isotopes	38
Most characteristic isotope
Electronic shell	[Xe] 4f6 6s2
The energy of the first ionization	542.3 kJ.mol-1
The energy of the second ionization	1066 kJ.mol-1
Discovery date	In 1853 by Jean Charles Galissard de Marignac, and in 1879 by Paul-Émile Lecoq de Boisbaudran

With the periodic table symbol Sm, atomic number 62, atomic mass of 150.35 g.mol-1, and electron configuration  [Xe] 4f6 6s2, samarium is a moderately soft metal with a silvery appearance. 

Samarium reaches its boiling point at 1794°C, 3261°F, 2067 K, while the melting point is reached at 1072°C, 1962°F, 1345 K. This member of the lanthanides family of elements has an electronegativity of 1.2 according to Pauling, whereas the atomic radius according to van der Waals is unknown.

This lanthanide has a rhombohedral crystal structure and possesses moderate paramagnetic properties above 109 K (−164 °C, −263 °F). When exposed to humid air, samarium readily oxidizes by forming a gray-yellow powder containing hydroxides and oxides. Also, Sm  spontaneously ignites at 150 °C.

How Was Samarium Discovered?

In 1785, the Swiss chemist Jean Charles Galissard de Marignac (1817–1894) observed unfamiliar lines in the mineral spectra while analysing a sample of didymium. It was very clear to him that there’s a new element in question, but this new element was not isolated until 1879.

After extracting ‘didymium’ from the mineral samarskite in his Paris laboratory, the French chemist Paul-Émile Lecoq de Boisbaudran (1838–1912) managed to produce ‘didymium’ nitrate solution. Next, he added ammonium hydroxide to the solution which resulted in two precipitates. One precipitate was made of didymium, while the other one was a samarium oxide. This impure oxide was identified as a new element by the sharp optical absorption lines detected by the spectroscopy method. 

How Did Samarium Get Its Name?

The name of this chemical element comes from the word “samaria”, a name of the samarium-rich mineral from which element 62 was first isolated. Later, Boisbaudran changed ‘samaria’ into ‘samarium’, thus honoring the discoverer of the mineral, the Russian mine official Colonel Vassili Samarsky-Bykhovets. 

Where Can You Find Samarium?

This rare-earth metal often occurs along with other minerals containing lanthanides, such as monazite sand, samarskite, bastnasite, cerite, and gadolinite. For commercial purposes, samarium is isolated from these minerals by ion exchange, electrochemical deposition, and solvent extraction techniques. The richest samarium deposits are located in China, Australia, United States, India, Brazil, and Sri Lanka. 

Samarium in Everyday Life

Element 62 has many applications in the fields of radiography, interferometry, high-resolution microscopy, holography, etc.

• Element 62 is used in electronics industries for production of headphones, catalysts, TV screens, carbon-arc lighting, and special types of glasses.
• Some samarium isotopes are used in dating of meteors and rocks.
• Samarium-cobalt magnets were popular during the 70s for reduction of the size of electronic items, such as the PC disk drives, cassette tape players, boom boxes, etc. These powerful permanent magnets (SmCo5) are also used in appliances that use microwave frequencies because they remain magnetic even at high temperatures.
• In medicine, samarium-153 is used in some cancer treatments to alleviate pain caused by the spreading metastasis.
• Samarium compounds act as sensitizers for phosphors excited in the infrared radiation.
• Sm2O3 acts as a catalyst for the dehydration and dehydrogenation of ethanol (C2H6O).
• Samarium oxide is used for doping of calcium fluoride crystals in optical lasers.
• Samarium-151 isotope participates in the nuclear fuel cycle as a neutron poison (or neutron absorber), as well as in infrared absorbing glass.
• Samarium-149 isotope is commonly used to control rods of nuclear reactors.
• When combined with neodymium, cerium, and lanthanum, i.e. in a mischmetal, samarium metal is applied in the production of flints. 

How Dangerous Is Samarium?

Its compounds are classified as highly toxic substances that may lead to adverse health effects. In addition, the dust particles of samarium metal present both a fire and explosion hazard.

Environmental Effects of Samarium

In its pure form, samarium has no biological role and poses no danger upon human’s health or the environment. 

Isotopes of Samarium

There are 38 observed forms of element 62. Naturally occurring amarium is made of five stable isotopes (144Sm, 149Sm, 150Sm, 152Sm and 154Sm) and two radioisotopes with exceptionally long half-life (147Sm with a half life of 1.06×1011 years, and 148Sm with a half-life of 7×1015 years). 

The isotopes of samarium decay by alpha decay, beta decay, and electron capture to isotopes of neodymium, promethium, and europium. 

Nuclide [n 1]	Z	N	Isotopic mass (Da) [n 2][n 3]	Half-life [n 4][n 5]	Decay mode [n 6]	Daughter isotope [n 7][n 8]	Spin and parity [n 9][n 5]	Natural abundance (mole fraction)
	Excitation energy[n 5]							Normal proportion	Range of variation
128Sm	62	66	127.95808(54)#	0.5# s			0+
129Sm	62	67	128.95464(54)#	550(100) ms			5/2+#
130Sm	62	68	129.94892(43)#	1# s	β+	130Pm	0+
131Sm	62	69	130.94611(32)#	1.2(2) s	β+	131Pm	5/2+#
					β+, p (rare)	130Nd
132Sm	62	70	131.94069(32)#	4.0(3) s	β+	132Pm	0+
					β+, p	131Nd
133Sm	62	71	132.93867(21)#	2.90(17) s	β+	133Pm	(5/2+)
					β+, p	132Nd
134Sm	62	72	133.93397(21)#	10(1) s	β+	134Pm	0+
135Sm	62	73	134.93252(17)	10.3(5) s	β+ (99.98%)	135Pm	(7/2+)
					β+, p (.02%)	134Nd
136Sm	62	74	135.928276(13)	47(2) s	β+	136Pm	0+
137Sm	62	75	136.92697(5)	45(1) s	β+	137Pm	(9/2−)
138Sm	62	76	137.923244(13)	3.1(2) min	β+	138Pm	0+
139Sm	62	77	138.922297(12)	2.57(10) min	β+	139Pm	1/2+
140Sm	62	78	139.918995(13)	14.82(12) min	β+	140Pm	0+
141Sm	62	79	140.918476(9)	10.2(2) min	β+	141Pm	1/2+
142Sm	62	80	141.915198(6)	72.49(5) min	β+	142Pm	0+
143Sm	62	81	142.914628(4)	8.75(8) min	β+	143Pm	3/2+
144Sm	62	82	143.911999(3)	Observationally Stable[n 10]			0+	0.0307(7)
145Sm	62	83	144.913410(3)	340(3) d	EC	145Pm	7/2−
146Sm	62	84	145.913041(4)	6.8(7)×107 y	α	142Nd	0+	Trace
147Sm[n 11][n 12][n 13]	62	85	146.9148979(26)	1.06(2)×1011 y	α	143Nd	7/2−	0.1499(18)
148Sm[n 11]	62	86	147.9148227(26)	7(3)×1015 y	α	144Nd	0+	0.1124(10)
149Sm[n 12][n 14]	62	87	148.9171847(26)	Observationally Stable[n 15]			7/2−	0.1382(7)
150Sm	62	88	149.9172755(26)	Observationally Stable[n 16]			0+	0.0738(1)
151Sm[n 12][n 14]	62	89	150.9199324(26)	88.8(24) y	β−	151Eu	5/2−
152Sm[n 12]	62	90	151.9197324(27)	Observationally Stable[n 17]			0+	0.2675(16)
153Sm[n 12]	62	91	152.9220974(27)	46.284(4) h	β−	153Eu	3/2+
154Sm[n 12]	62	92	153.9222093(27)	Observationally Stable[n 18]			0+	0.2275(29)
155Sm	62	93	154.9246402(28)	22.3(2) min	β−	155Eu	3/2−
156Sm	62	94	155.925528(10)	9.4(2) h	β−	156Eu	0+
157Sm	62	95	156.92836(5)	8.03(7) min	β−	157Eu	(3/2−)
158Sm	62	96	157.92999(8)	5.30(3) min	β−	158Eu	0+
159Sm	62	97	158.93321(11)	11.37(15) s	β−	159Eu	5/2−
160Sm	62	98	159.93514(21)#	9.6(3) s	β−	160Eu	0+
161Sm	62	99	160.93883(32)#	4.8(8) s	β−	161Eu	7/2+#
162Sm	62	100	161.94122(54)#	2.4(5) s	β−	162Eu	0+
163Sm	62	101	162.94536(75)#	1# s	β−	163Eu	1/2−#
164Sm	62	102	163.94828(86)#	500# ms	β−	164Eu	0+
165Sm	62	103	164.95298(97)#	200# ms	β−	165Eu	5/2−#

Source: Wikipedia

List of Samarium Compounds 

Unlike the other rare-earth elements, samarium mostly adopts the +2 oxidation state in a compound. When exposed to oxygen, water, or hydrogen ions, this chemical element reacts rapidly as the Sm2+ ion is a powerful reducing agent. 

The following is a list of most common compounds of samarium:

• Florencite-(Sm)
• Monazite-(Sm)
• Samarium (153Sm) lexidronam
• Samarium hexaboride
• Samarium monochalcogenides
• Samarium–cobalt magnet
• Samarium(II) bromide
• Samarium(II) chloride
• Samarium(II) fluoride
• Samarium(II) iodide
• Samarium(III) bromide
• Samarium(III) chloride
• Samarium(III) fluoride
• Samarium(III) hydroxide
• Samarium(III) oxide
• Samarium(III) sulfide

5 Interesting Facts and Explanations

1. Samarium is the first element of the periodic table that has been named in honor of a person.
2. Chemical elements classified in the lanthanide series are not really so rare in the Earth’s crust. The fact that it can be very difficult to separate these elements from each other makes the procedure hard, long, and expensive. In this way, smaller quantities of the rare earth elements can be obtained which makes them rare.
3. Samarium-cobalt magnets have the highest resistance to demagnetisation of any material that has ever been sytheticized. 
4. The French chemist Paul-Émile Lecoq de Boisbaudran, who is credited as the discoverer of samarium, also discovered the chemical element gallium. He also succeeded in isolating two other chemicals – gadolinium and dysprosium. 
5. Colonel Vassili Samarsky-Bykhovets was the first person to offer a sample of the mineral to Boisbaudran for his studies.