Tc 43

Technetium (Tc)

transition-metal

Period: 5 Group: 7 Block: s

Solid

Standard Atomic Weight

Electron configuration

[Kr] 5s² 4d⁵

Melting point

2156.85 °C (2430 K)

Boiling point

4264.85 °C (4538 K)

Density

1.100000e+4 kg/m³

Oxidation states

−3, −1, +1, +2, +3, +4, +5, +6, +7

Electronegativity (Pauling)

1.9

Ionization energy (1st)

Discovery year

1937

Atomic radius

135 pm

Details

Name origin Greek: technêtos (artificial).

Discovery country Italy

Discoverers Carlo Perrier, Émillo Segrè

Technetium is a radioactive transition metal in group 7, between molybdenum and ruthenium. It was the first element discovered without a stable isotope. Only trace natural technetium occurs, mainly from spontaneous fission of uranium and from neutron capture processes; practical quantities are made artificially. Its chemistry resembles rhenium and manganese in several oxidation states, and the isotope ⁹⁹ᵐTc is central to diagnostic nuclear medicine.

Technetium is a silvery-gray metal that tarnishes slowly in moist air. The common oxidation states of technetium are +7, +5, and +4. Under oxidizing conditions technetium (VII) will exist as the pertechnetate ion, TcO4-. The chemistry of technetium is said to be similar to that of rhenium. Technetium dissolves in nitric acid, aqua regia, and concentrated sulfuric acid, but is not soluble in hydrochloric acid of any strength. The element is a remarkable corrosion inhibitor for steel. The metal is an excellent superconductor at 11K and below.

Technetium was the first artificially produced element. It was isolated by Carlo Perrier and Emilio Segrè in 1937. Technetium was created by bombarding molybdenum atoms with deuterons that had been accelerated by a device called a cyclotron. Today, technetium is produced by bombarding molybdenum-98 with neutrons. Molybdenum-98 becomes molybdenum-99 when it captures a neutron. Molybdenum-99, with a half-life of 65.94 hours, decays into technetium-99 through beta decay. While technetium has never been found to occur naturally on earth, its spectral lines have been observed in S-, M- and N-type stars.

Technetium's most stable isotope, technetium-98, has a half-life of about 4,200,000 years. It decays into ruthenium-98 through beta decay.

From the Greek word technetos, artificial. Element 43 was predicted on the basis of the periodic table, and was erroneously reported as having been discovered in 1925, at which time it was named masurium. The element was actually discovered by Perrier and Segre in Italy in 1937. It was also found in a sample of molybdenum sent by E. Lawrence that was bombarded by deuterons in the Berkeley cyclotron. Technetium was the first element to be produced artificially. Since its discovery, searches for the element in terrestrial material have been made. Finally in 1962, technetium-99 was isolated and identified in African pitchblende (a uranium rich ore) in extremely minute quantities as a spontaneous fission product of uranium-238 by B.T. Kenna and P.K. Kuroda. If it does exist, the concentration must be very small. Technetium has been found in the spectrum of S-, M-, and N-type stars, and its presence in stellar matter is leading to new theories of the production of heavy elements in the stars.

Read about Technetium on Wikipedia

Images

Properties

Physical

Atomic radius (empirical) 135 pm

Covalent radius 147 pm

Van der Waals radius 209 pm

Metallic radius 127 pm

Density

Molar volume 0.0085 L/mol

Phase at STP solid

Melting point 2156.85 °C

Boiling point 4264.85 °C

Thermal conductivity 50.6 W/(m·K)

Crystal structure hcp

Chemical

Electronegativity (Pauling) 1.9

Electronegativity (Allen) 1.51

Electron affinity

Ionization energy (1st)

Ionization energy (2nd)

Ionization energy (3rd)

Ionization energy (4th)

Ionization energy (5th)

Oxidation states −3, −1, +1, +2, +3, +4, +5, +6, +7

Valence electrons 7

Electron configuration

Electron configuration (semantic)

Thermodynamic

Heat of fusion 0.24667047 eV

Heat of vaporization 5.182153 eV

Heat of sublimation 6.063119 eV

Heat of atomization 6.063119 eV

Atomization enthalpy

Nuclear

Stable isotopes 0

Mass number (most stable) 98

Discovery year 1937

Abundance

N/A

Reactivity

N/A

Crystal Structure

Lattice constant a 274 pm

Electronic Structure

Electrons per shell 2, 8, 18, 13, 2

Identifiers

CAS number 7440-26-8

Term symbol

InChI InChI=1S/Tc

InChI Key GKLVYJBZJHMRIY-UHFFFAOYSA-N

Electron Configuration Measured

Ion charge

Protons 43

Electrons 43

Charge Neutral

Configuration Tc: 4d⁵ 5s²

[Kr] 4d⁵ 5s²

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s²

Orbital diagram

↑↓

2/2

↑↓

2/2

↑↓

6/6

↑↓

2/2

↑↓

6/6

↑↓

2/2

↑↓

10/10

↑↓

6/6

↑↓

2/2

↑

5/10 5↑

Total electrons: 43 Unpaired: 5

Atomic model

Protons 43

Neutrons 67

Electrons 43

Mass number 110

Stability Radioactive

Isotopes change neutron count, mass, and stability — not the electron configuration of a neutral atom.

Schematic atomic model, not to scale.

Atomic Fingerprint

Emission / Absorption Spectrum

Emission Visible: 380–750 nm

Isotope Distribution

No stable isotopes.

Mass number	Atomic mass (u)	Natural abundance	Half-life
109 Radioactive	108.920256 ± 0.00001	N/A	905 ms
110 Radioactive	109.923744 ± 0.00001	N/A	900 ms
111 Radioactive	110.925901 ± 0.000011	N/A	350 ms
112 Radioactive	111.9299458 ± 0.000006	N/A	323 ms
94 Radioactive	93.9096536 ± 0.0000044	N/A	293 minutes

Measured

Phase / State

Solid 25 °C (298.15 K)

Reason: 2131.8 °C below melting point (2156.85 °C)

Melting point 2156.85 °C

Boiling point 4264.85 °C

Below melting by 2131.8 °C

0 K Current temperature: 25 °C 6000 K

Phase timeline

Schematic, not to scale

Solid

Liquid

Gas

Melting

Boiling

25°C

Solid

Liquid

Gas

Current

Phase transition points

Melting point Literature

2156.85 °C

Boiling point Literature

4264.85 °C

Current phase Calculated
Solid

Transition energies

Heat of fusion Literature

0.24667047 eV

Energy required to melt 1 mol at melting point

Heat of vaporization Literature

5.182153 eV

Energy required to vaporize 1 mol at boiling point

Heat of sublimation Literature

6.063119 eV

Energy required to sublime 1 mol at sublimation point

Density

Reference density Literature

1.100000e+4 kg/m³

At standard conditions

Current density Calculated

1.100000e+4 kg/m³

At standard conditions

Atomic Spectra

Showing 10 of 43 Atomic Spectra. Sorted by ion charge (ascending).

Lines Holdings ?

Ion	Charge	Total lines	Transition probabilities	Level designations
Tc I	0	600	13	561
Tc II	+1	40	6	23

NIST Lines Holdings →

Levels Holdings ?

Ion	Charge	Levels
Tc I	0	290
Tc II	+1	34
Tc III	+2	2
Tc IV	+3	2
Tc V	+4	2
Tc VI	+5	2
Tc VII	+6	2
Tc VIII	+7	2
Tc IX	+8	2
Tc X	+9	2

NIST Levels Holdings →

43 Tc 98

Technetium — Atomic Orbital Visualizer

[Kr]5s24d5

Energy levels 2 8 18 13 2

Oxidation states -3, -1, +1, +2, +3, +4, +5, +6, +7

HOMO 4d n=4 · l=2 · m=-2

Technetium — Atomic Orbital Visualizer Preview

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43 Tc 98

Technetium — Crystal Structure Visualizer

Primitive Hexagonal · Pearson hP2

Experimental

Pearson hP2

Coord. № 12

Packing 75.388%

Technetium — Crystal Structure Visualizer Preview

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Ionic Radii

Charge	Coordination	Spin	Radius
+4	6	N/A	64.5 pm
+5	6	N/A	60 pm
+7	4	N/A	37 pm
+7	6	N/A	56.00000000000001 pm

Compounds

96.906 u

98.906 u

93.910 u

96.906 u

95.908 u

97.907 u

100.907 u

Tc+4

96.906 u

92.910 u

Tc+7

96.906 u

103.911 u

Tc+4

98.906 u

Tc+6

96.906 u

Tc+5

96.906 u

94.908 u

89.924 u

99.908 u

Tc+7

98.906 u

Tc+7

93.910 u

85.945 u

Tc+6

98.906 u

Isotopes (5)

Twenty-two isotopes of technetium with masses ranging from 90 to 111 are reported. All the isotopes of technetium are radioactive. It is one of two elements with Z < 83 that have no stable isotopes; the other element is promethium (Z = 61). Technetium has three long lived radioactive isotopes: 97Tc (T1/2 = 2.6 x 106 years), 98Tc (T1/2 = 4.2 x 106 years) and 99Tc (T1/2 = 2.1 x 105 years). 95Tcm ("m" stands for meta state) (T1/2 = 61 days) is used in tracer work. However, the most useful isotope of technetium is 99Tcm (T1/2 = 6.01 hours) is used in many medical radioactive isotope tests because of its half-life being short, the energy of the gamma ray it emits, and the ability of technetium to be chemically bound to many biologically active molecules. Because 99Tc is produced as a fission product from the fission of uranium in nuclear reactors, large quantities have been produced over the years. There are kilogram quantities of technetium currently existing.

Mass number	Atomic mass (u)	Natural abundance	Half-life	Decay mode
109 Radioactive	108.920256 ± 0.00001	N/A	905 ms	β- =100%β-n =0.08±0.2%
110 Radioactive	109.923744 ± 0.00001	N/A	900 ms	β- =100%β-n =0.04±0.2%
111 Radioactive	110.925901 ± 0.000011	N/A	350 ms	β- =100%β-n =0.85±2%
112 Radioactive	111.9299458 ± 0.000006	N/A	323 ms	β- =100%β-n =1.5±0.2%
94 Radioactive	93.9096536 ± 0.0000044	N/A	293 minutes	β+ =100%

109 Radioactive

Atomic mass (u) 108.920256 ± 0.00001

Natural abundance N/A

Half-life 905 ms

Decay mode

β- =100%β-n =0.08±0.2%

110 Radioactive

Atomic mass (u) 109.923744 ± 0.00001

Natural abundance N/A

Half-life 900 ms

Decay mode

β- =100%β-n =0.04±0.2%

111 Radioactive

Atomic mass (u) 110.925901 ± 0.000011

Natural abundance N/A

Half-life 350 ms

Decay mode

β- =100%β-n =0.85±2%

112 Radioactive

Atomic mass (u) 111.9299458 ± 0.000006

Natural abundance N/A

Half-life 323 ms

Decay mode

β- =100%β-n =1.5±0.2%

94 Radioactive

Atomic mass (u) 93.9096536 ± 0.0000044

Natural abundance N/A

Half-life 293 minutes

Decay mode

β+ =100%

Spectral Lines

Showing 50 of 277 Spectral Lines. Only spectral lines with measured intensity are shown by default.

Wavelength (nm)	Intensity	Ion stage	Type	Transition	Accuracy	Source
485.359 nm	20000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4F*	Measured	NIST
409.5662 nm	15000	Tc I	emission	4d6.(5D).5s 6D → 4d6.(5D).5p 6D*	Measured	NIST
408.8702 nm	10000	Tc I	emission	4d6.(5D).5s 6D → 4d6.(5D).5p 6D*	Measured	NIST
411.5065 nm	10000	Tc I	emission	4d6.(5D).5s 6D → 4d6.(5D).5p 6D*	Measured	NIST
416.5605 nm	10000	Tc I	emission	4d6.(5D).5s 4D → 4d5.(6S).5s.(5S).5p 4P*	Measured	NIST
426.2245 nm	10000	Tc I	emission	4d5.5s2 6S → 4d5.(6S).5s.(7S).5p 6P*	Measured	NIST
429.7034 nm	10000	Tc I	emission	4d5.5s2 6S → 4d5.(6S).5s.(7S).5p 6P*	Measured	NIST
452.283 nm	10000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4D*	Measured	NIST
474.0602 nm	10000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4F*	Measured	NIST
482.0744 nm	10000	Tc I	emission	4d5.(6S).5s.(7S).5p 8P* → 4d5.(6S).5s.(7S).6s e 8S	Measured	NIST
486.6732 nm	10000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4F*	Measured	NIST
412.4217 nm	8000	Tc I	emission	4d6.(5D).5s 6D → 4d6.(5D).5p 6D*	Measured	NIST
489.1909 nm	8000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4F*	Measured	NIST
414.4961 nm	6000	Tc I	emission	4d6.(5D).5s 6D → 4d6.(5D).5p 6D*	Measured	NIST
417.2523 nm	5000	Tc I	emission	4d6.(5D).5s 6D → 4d6.(5D).5p 6D*	Measured	NIST
497.6341 nm	5000	Tc I	emission	4d5.(6S).5s.(7S).5p 8P* → 4d5.(6S).5s.(7S).6s e 8S	Measured	NIST
509.6269 nm	5000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 6F*	Measured	NIST
417.0266 nm	4000	Tc I	emission	4d6.(5D).5s 6D → 4d6.(5D).5p 6D*	Measured	NIST
477.1539 nm	4000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4F*	Measured	NIST
414.5126 nm	3000	Tc I	emission	4d6.(5D).5s 6D → 4d6.(5D).5p 6D*	Measured	NIST
448.7049 nm	3000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4D*	Measured	NIST
463.7499 nm	3000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4D*	Measured	NIST
394.709 nm	2000	Tc I	emission	4d6.(3H).5s 4H → 4d6.(3H).5p 2I*	Measured	NIST
399.4498 nm	2000	Tc I	emission	4d6.(3H).5s 4H → 4d6.(3H).5p 4G*	Measured	NIST
402.0759 nm	2000	Tc I	emission	4d6.(3H).5s 2H → 4d6.(3H).5p 2H*	Measured	NIST
453.9513 nm	2000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4D*	Measured	NIST
456.4541 nm	2000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4D*	Measured	NIST
464.8328 nm	2000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4D*	Measured	NIST
466.9303 nm	2000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4P*	Measured	NIST
471.7758 nm	2000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4F*	Measured	NIST
490.9509 nm	2000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4F*	Measured	NIST
517.4813 nm	2000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 6F*	Measured	NIST
383.7565 nm	1500	Tc I	emission	4d6.(3H).5s 4H → 4d6.(3H).5p 4I*	Measured	NIST
564.2116 nm	1500	Tc I	emission	4d6.(3F2).5s 4F → 4d6.(5D).5p 4D*	Measured	NIST
386.8248 nm	1000	Tc I	emission	4d6.(3H).5s 4H → 4d6.(3H).5p 4I*	Measured	NIST
401.1998 nm	1000	Tc I	emission	4d6.(3H).5s 4H → 4d5.(4D).5s.(5D).5p 6F*	Measured	NIST
403.9232 nm	1000	Tc I	emission	4d6.(3H).5s 4H → 4d6.(3H).5p 4G*	Measured	NIST
411.0214 nm	1000	Tc I	emission	4d6.(1I).5s 2I → 4d6.(1I).5p 2K*	Measured	NIST
412.8263 nm	1000	Tc I	emission	4d5.5s2 4G → 4d5.(4G).5s.(5G).5p 4H*	Measured	NIST
416.966 nm	1000	Tc I	emission	4d6.(3H).5s 4H → 4d5.(4G).5s.(5G).5p 4H*	Measured	NIST
417.6253 nm	1000	Tc I	emission	4d6.(5D).5s 6D → 4d6.(5D).5p 6D*	Measured	NIST
426.2682 nm	1000	Tc I	emission	4d6.(5D).5s 4D → 4d5.(6S).5s.(5S).5p 4P*	Measured	NIST
442.9581 nm	1000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4D*	Measured	NIST
448.1534 nm	1000	Tc I	emission	4d6.(3H).5s 2H → 4d6.(3H).5p 4H*	Measured	NIST
451.5974 nm	1000	Tc I	emission	4d6.(3H).5s 2H → 4d6.(3H).5p 4H*	Measured	NIST
455.7038 nm	1000	Tc I	emission	4d6.(3F2).5s 4F → 4d6.(3F2).5p 4G*	Measured	NIST
457.8438 nm	1000	Tc I	emission	4d6.(3G).5s 4G → 4d6.(3H).5p 2I*	Measured	NIST
459.3334 nm	1000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4D*	Measured	NIST
461.6842 nm	1000	Tc I	emission	4d5.(6S).5s.(7S).5p 6P* → 4d5.(6S).5s.(7S).5d f 6D	Measured	NIST
463.0527 nm	1000	Tc I	emission	4d6.(5D).5s 4D → 4d6.(5D).5p 4D*	Measured	NIST

Extended Properties

Covalent Radii (Extended)

Covalent radius (Pyykkö)

Covalent radius (Pyykkö, double)

Covalent radius (Pyykkö, triple)

Van der Waals Radii

Batsanov

Alvarez

UFF

MM3

Atomic & Metallic Radii

Atomic radius (Rahm)

Metallic radius (C12)

Numbering Scales

Mendeleev

Pettifor

Glawe

Electronegativity Scales

Ghosh

Miedema

Gunnarsson–Lundqvist

Robles–Bartolotti

Polarizability & Dispersion

Dipole polarizability

Dipole polarizability (unc.)

C₆ (Gould–Bučko)

Miedema Parameters

Miedema molar volume

Miedema electron density

Phase Transitions & Allotropes

Melting point	2430.15 K
Boiling point	4535.15 K

Oxidation State Categories

+5 extended

+4 main

−1 extended

+7 main

+3 extended

+6 extended

−3 extended

+2 extended

+1 extended

Advanced Reference Data

Screening Constants (10)

n	Orbital	σ
1	s	0.891
2	p	4.0592
2	s	11.3718
3	d	14.647
3	p	16.6159
3	s	16.2088
4	d	30.118
4	p	27.1888
4	s	25.8016
5	s	35.7735

Crystal Radii Detail (4)

Charge	CN	r_crystal (pm)	Origin
4	VI	78.5	from r^3 vs V plots, from metallic oxides,
5	VI	74	estimated, from r^3 vs V plots,
7	IV	51
7	VI	70	Ahrens (1952) ionic radius,

Isotope Decay Modes (70)

Isotope	Mode	Intensity
83	p	—
83	B+	—
83	B+p	—
84	p	—
84	B+	—
84	B+p	—
85	p	—
86	B+	100%
86	B+p	—
87	B+	100%

X‑ray Scattering Factors (508)

Energy (eV)	f₁	f₂
10	—	1.1689
10.1617	—	1.2263
10.3261	—	1.28651
10.4931	—	1.34968
10.6628	—	1.41595
10.8353	—	1.48547
11.0106	—	1.55841
11.1886	—	1.63493
11.3696	—	1.7152
11.5535	—	1.7906

Additional Data

Estimated Crustal Abundance

The estimated element abundance in the earth's crust.

Not Applicable

References (1)

[5] Technetium https://education.jlab.org/itselemental/ele043.html

Estimated Oceanic Abundance

The estimated element abundance in the earth's oceans.

Not Applicable

References (1)

[5] Technetium https://education.jlab.org/itselemental/ele043.html

References

(9)

1 PubChem

Data deposited in or computed by PubChem

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2 Atomic Mass Data Center (AMDC), International Atomic Energy Agency (IAEA)

The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.

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3 IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW)

Technetium

Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.

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4 IUPAC Periodic Table of the Elements and Isotopes (IPTEI)

The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.

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License note: Copyright (c) 2020 International Union of Pure and Applied Chemistry. The International Union of Pure and Applied Chemistry (IUPAC) contribution within Pubchem is provided under a CC-BY-NC-ND 4.0 license, unless otherwise stated.

5 Jefferson Lab, U.S. Department of Energy

Technetium

Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/

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License note: Please see citation and linking information: https://education.jlab.org/faq/index.html

6 Los Alamos National Laboratory, U.S. Department of Energy

Technetium

The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.

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7 NIST Physical Measurement Laboratory

Technetium

The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database

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8 PubChem Elements

Technetium

This section provides all form of data related to element Technetium.

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9 PubChem Elements

Technetium

The element property data was retrieved from publications.

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Last updated: May 1, 2026

Data verified: May 12, 2026

Content is reviewed against latest scientific data.