Tantalum (Ta)

Tantalum is a chemical element with the atomic number 73 in the periodic table. Its occurrence in Earth’s crust amounts to around 2 ppm. Being a member of the transition metals family of elements, this heavy metal has five valence electrons. 

It’s often used for its strong anti-corrosive and high thermal resistance properties in medicine, as well as in the chemical industry. Today, tantalum’s most popular application is in the production of tantalum capacitors for portable electronic equipment, such as mobile phones, DVD players, and computers. 

Chemical and Physical Properties of Tantalum

Property	Value
The symbol in the periodic table of elements	Ta
Atomic number	73
Atomic weight (mass)	180.95 g.mol-1
Group number	(Transition metals)
Period	6 (d-block)
Color	A greyish-blue metal with silver luster
Physical state	Solid at room temperature
Half-life	–
Electronegativity according to Pauling	1.5
Density	16.69 g.cm-3 at 20°C
Melting point	3017°C, 5463°F, 3290 K
Boiling point	5455°C, 9851°F, 5728 K
Van der Waals radius	0.1425 nm
Ionic radius	0.070 nm (+5)
Isotopes	35
Most characteristic isotope	–
Electronic shell	[Xe] 4f145d36s2
The energy of the first ionization	–
The energy of the second ionization	–
Discovery date	In 1802 by Anders Gustaf Ekenberg

With the periodic table symbol Ta, atomic number 73, atomic mass of 180.95 g.mol-1, and electron configuration [Xe] 4f145d36s2, tantalum is a hard, ductile, and dense greyish-blue heavy metal with a silver luster. It reaches its boiling point at 5455°C, 9851°F, 5728 K, while the melting point is achieved at 3017°C, 5463°F, 3290 K. 

Tantalum is a member of the transition metals family of elements in the periodic table and has an electronegativity of 1.5 according to Pauling, whereas the atomic radius according to van der Waals is 0.1425 nm.

This transition metal has a body-centered cubic structure. When exposed to temperatures lower than 150°C, element 73 can resist almost any chemical attack. Tantalum is attacked only by hydrofluoric acid, acidic solutions containing the fluoride ion, and free sulfur trioxide.

Tantalum also has excellent anti-corrosive properties and forms a protective oxide film (Ta2O5) on its surface. In addition, this chemical element is also characterized by good electrical and heat conductivity.

How Was Tantalum Discovered?

While conducting chemical analysis of the mineral samples tantalite (obtained from Finland) and yttrotantalite (obtained from Sweden), the Swedish analytical chemist  Anders Gustaf Ekenberg (1767 – 1813) was convinced that he had succeeded in discovering element 67 of the periodic table. He published his scientific evidence in 1802.

But, the English chemist William Hyde Wollaston didn’t agree with Ekenberg’s findings. He believed that the new element is actually niobium, not tantalum. Being a respected scientist, his opinion influenced the entire scientific community. However, Wollaston’s claims turned out to be erroneous due to the fact that tantalum and niobium are extremely hard to separate from one another. 

In 1846 the German mineralogist Heinrich Rose (1795 – 1864) succeeded in distinguishing niobium and tantalum as two separate chemical elements, thus rejecting the long-held theory in the scientific circles that tantalum and niobium were identical elements.

Finally, in 1844 the Swiss chemist Jean Charles Galissard de Marignac confirmed Rose’s findings and isolated tantalum and niobium as two distinct elements. In this way, de Marignac brought the Swedish analytical chemist Anders Ekeberg the well-deserved acknowledgment as the first chemist to discover element 67. 

Pure tantalum was produced in 1903 by the German chemist and materials scientist Werner von Bolton (1868 – 1912). 

How Did Tantalum Get Its Name?

The name of this chemical element comes from the Greek mythological character King Tantalus (or Tantalos). According to Greek mythology, King Tantalus had a daughter named Niobe. 

Since element 67 and element 41 are difficult to be separated from each other in mineral ore, these two elements were associated with the mythological father-daughter relationship and got the names tantalum (after Tantalus) and niobium (after Niobe). 

Where Can You Find Tantalum?

Tantalum mostly occurs in the minerals coltan and columbite-tantalite. Tantalite ores also contain minerals and metals such as samarskite, niobium, manganese, and iron. The extensive list of tantalum-rich minerals also includes:

• Achalaite
• Béhierite
• Betafite
• Billwiseite
• Euxenite
• Microlite
• Polycrase
• Rynersonite
• Samarskite-(Y)
• Simpsonite
• Stibiotantalite
• Tantite
• Tapiolite
• Titanowodginite
• Wodginite
• Zimbabweite

Canada, Congo, Portugal, Rwanda, China, and Brazil, are some of the tantalum-producing countries rich in pyrochlore ores (another mineral source of the elements niobium and tantalum). Since these two elements are hard to separate, various techniques are used for their isolation. They include either electrolysis, reduction of potassium fluorotantalate with sodium, or reacting the carbide with oxide. Metallic tantalum is produced by powder metallurgy techniques.

Tantalum is also produced in Thailand and Malaysia as a by-product of tin mining. Brazil, Australia, and Mozambique are the top three countries in the world that hold the largest tantalum reserves. Australia’s areas Wodgina and the Greenbushes are locations where the world’s richest tantalum deposits are found. 

Tantalum in Everyday Life

Mainly for its superb corrosion resistance, this substance is highly applicable in objects that need to sustain high temperatures, the production of electrical devices, the manufacturing of medical implants, and chemical industry processes that employ highly corrosive chemicals. 

• The strong anti-corrosive properties of tantalum are used for making surgical implants, aircraft engines (jet engines), and capacitors;
• Tantalum is used in a variety of alloys to add high strength, ductility, and a high melting point;
• As a result of its ductility, tantalum metal can be drawn into fine wires or filaments, which are later applied for evaporation of metals like aluminum;
• The high melting point of this chemical element makes it suitable for the production of high-temperature devices, surgical equipment, electrolytic capacitors, vacuum furnace parts, heat exchangers, and chemical equipment;
• Tantalum also has a wide application in the manufacturing of refractive index glass, camera lenses, and electron tubes;
• Tantalum oxide is used in the production of mobile phone capacitors. Namely, tantalum capacitors have an extremely high capacitance packed in a small volume which is perfectly suitable for manufacturing smaller electronic gadgets;
• Element 73 is commonly applied in the making of non-ferrous alloys for missiles, and nuclear reactors.

How Dangerous Is Tantalum?

Pure tantalum is a moderately toxic substance. The ongoing studies are still trying to derive evidence whether this chemical element is a carcinogen, i.e. tumor-causing substance. Also, cases of tantalum poisoning after prolonged exposure to high concentrations have not yet been reported. 

Tantalum pentoxide is a colorless solid that gives off volatile reactions with oxidizers, which may present both an explosion and fire hazard. 

Environmental Effects of Tantalum

If tantalum waste is uncontrollably released, it may lead to severe pollution of the geological, biological, or aquatic systems of our environment. Industries that process tantalum may contaminate the air and waters with tantalum, which may further trigger adverse health effects.

Isotopes of Tantalum

There are xx observed isotopes of tantalum. Naturally occurring tantalum (73Ta) is made up of two stable isotopes: 181Ta (with 99.988% natural occurrence) and 180mTa (with 0.012% natural occurrence).

Tantalum has also 35 synthetically produced radioisotopes. Among them, tantalum-179 is the longest living radioactive isotope of this chemical element with a half-life of 1.82 years. 

All forms of element 67 decay in alpha mode, beta mode, via proton emission or isomeric transition to elements Hf, Lu, W, and Ta. 

Nuclide [n 1]	Z	N	Isotopic mass (Da) [n 2][n 3]	Half-life [n 4]	Decay mode [n 5]	Daughter isotope [n 6][n 7]	Spin and parity [n 8][n 4]	Natural abundance (mole fraction)
	Excitation energy[n 4]							Normal proportion	Range of variation
155 Ta	73	82	154.97459(54)#	13(4) µs [12(+4−3) µs]			(11/2−)
156 Ta	73	83	155.97230(43)#	144(24) ms	β+ (95.8%)	156Hf	(2−)
					p (4.2%)	155Hf
157 Ta	73	84	156.96819(22)	10.1(4) ms	α (91%)	153Lu	1/2+
					β+ (9%)	157Hf
158 Ta	73	85	157.96670(22)#	49(8) ms	α (96%)	154Lu	(2−)
					β+ (4%)	158Hf
159 Ta	73	86	158.963018(22)	1.04(9) s	β+ (66%)	159Hf	(1/2+)
					α (34%)	155Lu
160 Ta	73	87	159.96149(10)	1.70(20) s	α	156Lu	(2#)−
					β+	160Hf
161 Ta	73	88	160.95842(6)#	3# s	β+ (95%)	161Hf	1/2+#
					α (5%)	157Lu
162 Ta	73	89	161.95729(6)	3.57(12) s	β+ (99.92%)	162Hf	3+#
					α (.073%)	158Lu
163 Ta	73	90	162.95433(4)	10.6(18) s	β+ (99.8%)	163Hf	1/2+#
					α (.2%)	159Lu
164 Ta	73	91	163.95353(3)	14.2(3) s	β+	164Hf	(3+)
165 Ta	73	92	164.950773(19)	31.0(15) s	β+	165Hf	5/2−#
166 Ta	73	93	165.95051(3)	34.4(5) s	β+	166Hf	(2)+
167 Ta	73	94	166.94809(3)	1.33(7) min	β+	167Hf	(3/2+)
168 Ta	73	95	167.94805(3)	2.0(1) min	β+	168Hf	(2−,3+)
169 Ta	73	96	168.94601(3)	4.9(4) min	β+	169Hf	(5/2+)
170 Ta	73	97	169.94618(3)	6.76(6) min	β+	170Hf	(3)(+#)
171 Ta	73	98	170.94448(3)	23.3(3) min	β+	171Hf	(5/2−)
172 Ta	73	99	171.94490(3)	36.8(3) min	β+	172Hf	(3+)
173 Ta	73	100	172.94375(3)	3.14(13) h	β+	173Hf	5/2−
174 Ta	73	101	173.94445(3)	1.14(8) h	β+	174Hf	3+
175 Ta	73	102	174.94374(3)	10.5(2) h	β+	175Hf	7/2+
176 Ta	73	103	175.94486(3)	8.09(5) h	β+	176Hf	(1)−
177 Ta	73	104	176.944472(4)	56.56(6) h	β+	177Hf	7/2+
178 Ta	73	105	177.945778(16)	9.31(3) min	β+	178Hf	1+
179 Ta	73	106	178.9459295(23)	1.82(3) y	EC	179Hf	7/2+
180 Ta	73	107	179.9474648(24)	8.152(6) h	EC (86%)	180Hf	1+
					β− (14%)	180W
180m1 Ta	77.1(8) keV			Observationally stable[n 9][n 10]			9−	1.2(2)×10−4
181 Ta	73	108	180.9479958(20)	Observationally stable[n 11]			7/2+	0.99988(2)
182 Ta	73	109	181.9501518(19)	114.43(3) d	β−	182W	3−
183 Ta	73	110	182.9513726(19)	5.1(1) d	β−	183W	7/2+
184 Ta	73	111	183.954008(28)	8.7(1) h	β−	184W	(5−)
185 Ta	73	112	184.955559(15)	49.4(15) min	β−	185W	(7/2+)#
186 Ta	73	113	185.95855(6)	10.5(3) min	β−	186W	(2−,3−)
187 Ta	73	114	186.96053(21)#	2# min [>300 ns]	β−	187W	7/2+#
188 Ta	73	115	187.96370(21)#	20# s [>300 ns]	β−	188W
189 Ta	73	116	188.96583(32)#	3# s [>300 ns]			7/2+#
190 Ta	73	117	189.96923(43)#	0.3# s

Source: Wikipedia

List of Tantalum Compounds 

As a part of a compound, tantalum mostly occurs in the oxidation states that range from -3 to +5. It typically forms tantalates, carbides, fluorides, silicides, nitrides, and oxides. 

The following is a list of the most commonly prepared tantalum compounds:

• Pentakis(dimethylamido)tantalum
• Pentamethyltantalum
• Tantalcarbide
• Tantalum boride
• Tantalum carbide
• Tantalum hafnium carbide
• Tantalum nitride
• Tantalum pentafluoride
• Tantalum pentoxide
• Tantalum telluride
• Tantalum trialuminide
• Tantalum(III) chloride
• Tantalum(IV) sulfide
• Tantalum(V) bromide
• Tantalum(V) chloride
• Tantalum(V) ethoxide
• Tantalum(V) iodide

5 Interesting Facts and Explanations

1. In its pure elemental form, tantalum is a very soft substance.
2. When added to alloys, tantalum makes them more brittle. For this reason, element 67 is rarely added to metal alloys.
3. The English chemist who disputed Ekeberg’s discovery of tantalum, William Hyde Wollaston, has earned his reputation in the scientific community after discovering the chemical elements palladium and rhodium.
4. So far, tantalum and tantalum compounds have not been classified as presumptive, suspected, or possible triggers of cancer in humans in the U.S. federal registry of suspected human carcinogen substances.
5. Tantalum is a biocompatible and hypoallergenic metal, which means that it doesn’t cause skin allergies.