Element: Technetium

General data

Element name	Technetium
Chemical symbol	Tc
Atomic number Z	43
Year discovered	1937
Standard state (25°C)	Solid
Category	Transition metal
Block	d
Atomic mass	[97]
CPK color	#3B9E9E

Physical properties

Melting point	2430 K (2157 °C)
Boiling point	4538 K (4265 °C)
Density	11 g/cm³

Energy properties

First ionization energy	7.28 eV
Electron affinity	0.55 eV

Atomic structure

Protons	43 (Atomic number)
Neutrons (Tc-97, longest-lived isotope)	54
Electrons	43
Electron configuration	[Kr] 5s² 4d⁵
Oxidation states	+7, +6, +4
Electronegativity (Pauling)	1.9
Atomic radius (van der Waals)	209 pm

Ionization energies - NIST ASD (43 states)

State	Charge	Ioniz. energy (eV)	Type
Tc I	0+	7.11938 ± 0.00003	measured
Tc II	1+	15.26	semi-empirical
Tc III	2+	29.55	semi-empirical
Tc IV	3+	41 ± 1.7	calculated
Tc V	4+	57 ± 1.9	calculated
Tc VI	5+	72 ± 2	calculated
Tc VII	6+	88 ± 2	calculated
Tc VIII	7+	150 ± 2.1	calculated
Tc IX	8+	169 ± 2.2	calculated
Tc X	9+	189.9 ± 2.2	calculated
Tc XI	10+	214 ± 2.4	calculated
Tc XII	11+	239 ± 2.5	calculated
Tc XIII	12+	262.08 ± 0.12	semi-empirical
Tc XIV	13+	311 ± 3	calculated
Tc XV	14+	338.55 ± 0.17	semi-empirical
Tc XVI	15+	604 ± 3	calculated
Tc XVII	16+	655 ± 3	calculated
Tc XVIII	17+	713 ± 3	calculated
Tc XIX	18+	773 ± 3	calculated
Tc XX	19+	829 ± 4	calculated
Tc XXI	20+	904 ± 4	calculated
Tc XXII	21+	968 ± 4	calculated
Tc XXIII	22+	1032 ± 4	calculated
Tc XXIV	23+	1102 ± 4	calculated
Tc XXV	24+	1166 ± 4	calculated
Tc XXVI	25+	1354 ± 4	semi-empirical
Tc XXVII	26+	1411.6 ± 1.5	semi-empirical
Tc XXVIII	27+	1479.5 ± 2	semi-empirical
Tc XXIX	28+	1559 ± 6	semi-empirical
Tc XXX	29+	1638 ± 4	semi-empirical
Tc XXXI	30+	1689 ± 8	semi-empirical
Tc XXXII	31+	1838 ± 3	semi-empirical
Tc XXXIII	32+	1900.28 ± 0.06	semi-empirical
Tc XXXIV	33+	4505 ± 2.5	semi-empirical
Tc XXXV	34+	4681 ± 8	semi-empirical
Tc XXXVI	35+	4874 ± 10	semi-empirical
Tc XXXVII	36+	5060 ± 40	semi-empirical
Tc XXXVIII	37+	5361 ± 6	semi-empirical
Tc XXXIX	38+	5570 ± 4	semi-empirical
Tc XL	39+	5838 ± 6	semi-empirical
Tc XLI	40+	6008.391 ± 0.017	calculated
Tc XLII	41+	25004.531 ± 0.01	calculated
Tc XLIII	42+	25787.047 ± 0.016	calculated

Value type as given by NIST ASD: measured - from evaluated experimental data; calculated - from ab initio calculations (mostly highly ionised atoms that have not been measured; for the simplest ones, e.g. H I, the calculation is more accurate than measurement); semi-empirical - from interpolation, extrapolation or another semi-empirical method.

Photos

Photo of the element: Technetium (Tc) — © images-of-elements.com (CC BY 3.0)

Isotopes (38)

A	N	Half-life	Decay
Tc-85	42	< 100 ns	p
Tc-86	43	55 ms	EC/β⁺
Tc-87	44	2.1 s	EC/β⁺
Tc-88	45	6.4 s	EC/β⁺
Tc-89	46	12.8 s	EC/β⁺
Tc-90	47	49.2 s	EC/β⁺
Tc-91	48	3.14 min	EC/β⁺
Tc-92	49	4.23 min	EC/β⁺
Tc-93	50	2.78 h	EC/β⁺
Tc-94	51	293 min	EC/β⁺
Tc-95	52	19.26 h	EC/β⁺
Tc-96	53	4.27 d	EC/β⁺
Tc-97	54	4.21×10⁶ a	EC
Tc-98	55	4.2×10⁶ a	β⁻
Tc-99	56	2.111×10⁵ a	β⁻
Tc-100	57	15.65 s	β⁻
Tc-101	58	14.12 min	β⁻
Tc-102	59	5.28 s	β⁻
Tc-103	60	54.2 s	β⁻
Tc-104	61	18.2 min	β⁻
Tc-105	62	7.64 min	β⁻
Tc-106	63	35.7 s	β⁻
Tc-107	64	21.2 s	β⁻
Tc-108	65	5.15 s	β⁻
Tc-109	66	0.88 s	β⁻
Tc-110	67	0.911 s	β⁻
Tc-111	68	350 ms	β⁻
Tc-112	69	323 ms	β⁻
Tc-113	70	152 ms	β⁻
Tc-114	71	118 ms	β⁻
Tc-115	72	78 ms	β⁻
Tc-116	73	57 ms	β⁻
Tc-117	74	45 ms	β⁻
Tc-118	75	30 ms	β⁻
Tc-119	76	22 ms	β⁻
Tc-120	77	21 ms	β⁻
Tc-121	78	22 ms	β⁻
Tc-122	79	unknown	β⁻

Data sources

PubChem Periodic Table API - Retrieved on 29 June 2026 - licence: CC0
IUPAC CIAAW - Abridged Standard Atomic Weights 2024 - Table version: 2024 - licence: Public domain
NNDC Wallet Cards 2023 - Data as of 15 October 2024 - licence: Public domain
Images of Elements - Retrieved on 29 June 2026 - licence: CC BY 3.0

More about the data sources