Explore every known oxidation state of technetium (Tc, element 43), from -3 to +7, with real compounds, step-by-step assignments, and identification tips.
Atomic #43TcTechnetium
Atomic Mass
98 u (most stable)
Group
7 (VIIB)
Period
5
Block
d-block
Electron Config.
[Kr] 4d⁵ 5s²
Oxidation States
-3 to +7
Technetium exhibits oxidation states from −3 to +7. Click a state card to see
its compounds, identification method, and context.
Oxidation State −3
Technetium in the −3 state is rare and found only in selected organometallic or anionic carbonyl complexes where strong pi-acid ligands (such as CO) donate significant electron density back to the metal, making Tc formally electron-rich. The −3 state is not accessible under normal aqueous conditions.
How to Identify This State
Apply the standard rules: CO ligands are neutral, NO+ is +1. If the complex carries a negative charge and the ligand set is all CO or similarly neutral, solve: Tc + 0 × n(ligands) = overall charge. For [Tc(CO)4]3−: CO = 0 each; Tc = −3.
Example Compounds
Formula
Name
Assignment
Notes
[Tc(CO)4]3−
Tetracarbonyltechnetate(3-)
CO is neutral; charge = −3 → Tc = −3
Anionic organometallic species. Primarily of academic interest in establishing the lower boundary of Tc oxidation chemistry.
Common Uses
Academic reference for the full range of transition-metal oxidation states
Model systems for studying pi-back-bonding in d-block chemistry
Benchmarking computational methods for heavy transition metals
Oxidation State −1
The −1 state appears in carbonyl and nitrosyl anion complexes. Like the −3 state, it requires strong electron donors (pi-acid ligands) to stabilize the high electron density on technetium. These are low-valent, organometallic species.
How to Identify This State
In [TcH(CO)5]−: H in a metal hydride is −1, CO = 0. Overall charge = −1. Solving: Tc + (−1) + 5(0) = −1 → Tc = 0. The neutral hydride TcH(CO)5 itself gives Tc = −1 (H = −1 in metal hydrides, CO = 0, neutral molecule: Tc + (−1) = 0 → Tc = +1 — see Tc(+1) entry). For a strict −1 assignment, use purely carbonyl anions without H.
Example Compounds
Formula
Name
Assignment
Notes
[Tc2(CO)10]2−
Decacarbonyldirhenate analogue
CO = 0 × 10; charge = −2; 2 Tc atoms → each Tc = −1
Low-valent carbonyl anion complex; analogous to known carbonyl metalate anions of Mn and Re.
Common Uses
Organometallic synthesis and ligand exchange studies
Probing metal-ligand bonding in low-oxidation-state chemistry
Academic research on Group 7 carbonyl chemistry
Oxidation State 0
Elemental technetium is assigned oxidation state 0 by convention. It is a silver-gray, radioactive metal obtained as a by-product of uranium-235 fission in nuclear reactors. The Tc2(CO)10 neutral binuclear carbonyl also formally places Tc at 0 if the metal-metal bond is treated as non-polar.
How to Identify This State
Any pure metallic technetium or symmetric binuclear complex where ligands are neutral and there is no net charge: oxidation state is 0 by definition.
Example Compounds
Formula
Name
Assignment
Notes
Tc (metal)
Technetium metal
Elemental → Tc = 0
Radioactive, silver-gray transition metal. Produced in gram quantities as a fission product of U-235. Corrosion-resistant; melts at 2157 °C.
Tc2(CO)10
Ditechnetium decacarbonyl
CO = 0; no charge; Tc−Tc bond symmetrical → Tc = 0
Analogous to Mn₂(CO)₁₀. The Tc−Tc bond is non-polar; each Tc formally zero.
Common Uses
Corrosion studies (technetium metal inhibits steel corrosion)
Nuclear waste characterization (Tc-99 is a long-lived fission product)
Organometallic precursor synthesis (Tc₂(CO)₁₀ as starting material)
Oxidation State +1
Technetium(I) occurs in mixed carbonyl/phosphine and isonitrile complexes. The +1 state is stabilized by pi-acid ligands (CO, isonitriles, phosphines) that remove electron density from the metal via back-bonding. Several Tc(I) complexes have been studied as potential radiopharmaceutical scaffolds because they are kinetically inert and easy to functionalize.
How to Identify This State
In fac-[Tc(CO)3(H2O)3]+: CO = 0 (×3), H2O = 0 (×3), overall charge = +1 → Tc = +1. More generally: neutral ligands (CO, PR3, H2O) contribute 0; anionic ligands (Cl−, CN−) contribute −1 each; solve for Tc to match the complex charge.
Example Compounds
Formula
Name
Assignment
Notes
[Tc(CO)3(H2O)3]+
Fac-tricarbonylaquatechnetium(I)
3(0) + 3(0) = 0; charge = +1 → Tc = +1
Versatile radiopharmaceutical precursor ("Tc(CO)₃" core). Water ligands are easily displaced by targeting biomolecules.
[TcCl(CO)5]
Pentacarbonylchlorotechnetium(I)
CO = 0 × 5; Cl = −1; neutral molecule → Tc = +1
Organometallic Tc(I) precursor for substitution reactions.
Common Uses
Radiopharmaceutical design (Tc(CO)₃ core for SPECT imaging agents)
Organometallic synthesis of bifunctional chelators
Model systems for ligand-exchange kinetics in d-block chemistry
Oxidation State +3
Technetium(III) is an intermediate oxidation state accessible in halide and mixed-ligand complexes. It is a d4 configuration, which typically forms octahedral complexes. Tc(III) is less commonly encountered than Tc(IV) or Tc(VII) but appears in several radiopharmaceutically relevant precursors and in the reduction chemistry of pertechnetate.
Dark red solid; used as a starting material for Tc(III) coordination chemistry.
[TcCl3(dppe)]
Tc(III) phosphine complex
3(−1) + 0 + Tc = 0 → Tc = +3
dppe (bisphosphine) is neutral. Representative of Tc(III) in mixed halide/phosphine ligand sets.
Tc2Cl62−
Ditechnetate(III) complex
6(−1) + 2Tc = −2 → Tc = +3
Features a Tc−Tc single bond; Tc(III) d⁴ complex.
Common Uses
Precursors for Tc radiopharmaceutical chelate chemistry
Study of Tc-Tc metal-metal bonding in halide-bridged dimers
Intermediate in the reduction of pertechnetate for labeling procedures
Oxidation State +4
Technetium(IV) is the most stable solid-state oxidation state, analogous to MnO2. TcO2 is the dominant phase when Tc metal is mildly oxidized or when pertechnetate is reduced in non-aqueous media. The d3 configuration in Tc(IV) forms stable octahedral complexes. In nuclear waste chemistry, Tc(IV) sorption onto mineral surfaces is important for understanding technetium mobility in the environment.
How to Identify This State
In TcO2: O = −2 (×2 = −4); neutral compound → Tc = +4. In TcCl4: Cl = −1 (×4 = −4); neutral → Tc = +4. In [TcO2]2+: O = −2 × 2 = −4; charge = +2; Tc = +4 + 2 is wrong — re-examine: Tc + (−4) = +2 → Tc = +6 for that ion (this is Tc(VI)).
Example Compounds
Formula
Name
Assignment
Notes
TcO2
Technetium(IV) Oxide
O = −2 × 2 = −4; neutral → Tc = +4
Most stable bulk oxide of Tc. Black solid; formed when Tc metal oxidizes slowly. Insoluble in water; relevant to nuclear waste immobilization.
TcCl4
Technetium(IV) Chloride
Cl = −1 × 4 = −4; neutral → Tc = +4
Dark solid; readily hydrolyzes. Used as a precursor in coordination chemistry.
[TcCl6]2−
Hexachlorotechnetate(IV)
Cl = −1 × 6 = −6; charge = −2; Tc = +4
Classic d³ complex used to study optical spectra and bonding of Tc(IV).
Common Uses
Nuclear waste form chemistry (TcO₂ immobilized in glass or metal alloys)
Inorganic synthesis precursor for Tc coordination compounds
Study of Tc mobility in geological systems (sorption of Tc(IV) on minerals)
Reference standard for Tc speciation in environmental samples
Oxidation State +5
Technetium(V) is the oxidation state of greatest practical importance in radiopharmaceuticals. The [Tc=O]3+ oxo core (the "technetium-oxo" or "TcO" core) is kinetically stable and widely used to attach targeting ligands for SPECT imaging. Tc(V) is a d2 system that forms square-pyramidal or octahedral complexes with a terminal oxo ligand.
How to Identify This State
In [TcO(DMSA)2]−: O2− (the oxo ligand) = −2; 2 DMSA (dimercaptosuccinate) each carry charge −2 (total −4); overall = −1. Tc + (−2) + (−4) = −1 → Tc = +5. More generally: identify the oxo as O2−, account for anionic chelate charges, solve for Tc.
Example Compounds
Formula
Name
Assignment
Notes
[TcO(DMSA)2]−
Tc(V)-DMSA complex
Oxo = −2; 2 DMSA = −4; charge = −1 → Tc = +5
DMSA = dimercaptosuccinic acid. Used clinically as a kidney-imaging agent (Tc-99m DMSA).
[TcO(MAG3)]−
Tc(V)-MAG3 complex
Oxo = −2; MAG3 = −3; charge = −1 → Tc = +5
MAG3 = mercaptoacetylglycylglycylglycine. Widely used renal SPECT agent with high extraction efficiency.
TcOCl3
Oxotrichlorotechnetium(V)
O = −2; 3 Cl = −3; neutral → Tc = +5
Inorganic Tc(V) oxo halide; precursor for synthesis of Tc(V) chelate complexes.
Common Uses
Tc-99m DMSA: renal cortex imaging and childhood Wilms tumor staging
Tc-99m MAG3: renal function studies, obstructive uropathy assessment
Basis for design of bifunctional chelators in radiopharmaceutical chemistry
Model complexes for studying oxo-metal bonding in d² systems
Oxidation State +7
The highest and thermodynamically most stable oxidation state of technetium in aqueous media. Pertechnetate (TcO4−) is the form technetium adopts spontaneously in oxygenated water — analogous to permanganate (MnO4−) but far less oxidizing. Tc-99m as pertechnetate (Na99mTcO4) is the direct elution product of the Mo-99/Tc-99m generator and is used in thyroid, salivary gland, and gastric mucosa imaging without further chelation.
How to Identify This State
In TcO4−: O = −2 (×4 = −8); overall charge = −1 → Tc + (−8) = −1 → Tc = +7. In Tc2O7: O = −2 × 7 = −14; neutral → 2Tc = +14 → Tc = +7.
Example Compounds
Formula
Name
Assignment
Notes
TcO4−
Pertechnetate Ion
4(−2) + Tc = −1 → Tc = +7
Thermodynamically stable form in oxygenated water. The form produced directly by the Mo-99/Tc-99m generator. Used as-is for thyroid and gastric mucosa SPECT imaging.
KTcO4
Potassium Pertechnetate
4(−2) + Tc + (+1) = 0 → Tc = +7
White crystalline solid; slightly soluble in water. Used as a standard chemical source of pertechnetate in non-radioactive Tc chemistry.
Tc2O7
Technetium Heptoxide
7(−2) + 2Tc = 0 → Tc = +7
Yellow, volatile solid; the anhydride of pertechnetic acid (HTcO₄). Formed when Tc metal burns in excess O₂.
HTcO4
Pertechnetic Acid
4(−2) + (+1) + Tc = 0 → Tc = +7
Strong acid formed when Tc₂O₇ dissolves in water. Less oxidizing than HMnO₄ (permanganic acid).
Common Uses
Tc-99m pertechnetate: thyroid gland scintigraphy (competes with iodide uptake)
Thermodynamically stable in O₂/H₂O; Tc-99m pertechnetate generator product.
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Summary
Explore every known oxidation state of technetium (Tc, element 43), from -3 to +7, with real compounds, step-by-step assignments, and identification tips.
How it works
Click an oxidation state card to open its detail panel.
The detail panel shows a description, example compounds, step-by-step assignment, and identification tips.
Use the Compound Lookup tab to select a known technetium compound and see the oxidation state of Tc explained step by step.
Click any formula badge to copy it to your clipboard.
Switch between the Explorer and Compound Lookup tabs using the tab bar at the top.
The Summary table at the bottom lists all states with their stability and key example at a glance.
Use cases
Students studying d-block / transition-metal oxidation states for exams.
Nuclear medicine professionals understanding the chemistry of Tc-99m radiopharmaceuticals.
Inorganic chemistry researchers checking the oxidation state of Tc in a specific complex or reagent.
Teachers preparing reference materials on Group 7 or period-5 transition metals.
Chemists comparing oxidation-state trends across Mn, Tc, and Re in Group 7.
Frequently Asked Questions
Technetium has been observed in oxidation states ranging from -3 to +7. The most stable and common states in practice are +4 (in TcO2 and many complexes) and +7 (in the pertechnetate ion TcO4^-). States +1, +3, +5, and +6 occur in specific coordination compounds. States -1, -3, and 0 are known in organometallic or carbonyl chemistry.
Technetium-99m (a metastable nuclear isomer) emits a 140 keV gamma ray with a 6-hour half-life, making it nearly ideal for SPECT imaging — enough energy to penetrate tissue but short enough to limit patient dose. When reduced from Tc(VII)/pertechnetate to Tc(V) or Tc(IV) and chelated with appropriate ligands (e.g., HMPAO, MAA, MDP), it targets specific organs. It accounts for roughly 80% of all nuclear medicine procedures worldwide.
The pertechnetate ion has an overall charge of -1. Oxygen is -2 in this context (4 O atoms × -2 = -8). Solving: Tc + (-8) = -1 → Tc = -1 + 8 = +7. So technetium is +7 in TcO4^-.
Technetium is [Kr] 4d5 5s2 — a half-filled 4d shell plus a filled 5s. This is analogous to manganese ([Ar] 3d5 4s2). The half-filled d subshell confers additional exchange-energy stabilization, contributing to the relative stability of the +7 state when all valence electrons are removed.
Technetium sits at atomic number 43, which has an odd proton count. Combined with the specific neutron-to-proton ratios in the range Z=43, there is no combination that yields a stable nuclide. The longest-lived isotope is Tc-98 (half-life ~4.2 million years). All technetium on Earth is either produced artificially in nuclear reactors (as a fission product of U-235) or transiently exists in trace amounts in uranium ores.
Both are Group 7, so their maximum oxidation state is +7 (MnO4^- and TcO4^-). However, for technetium the +7 state (pertechnetate) is more stable relative to lower states than permanganate (Mn +7), which is a powerful oxidant. Tc also shows a more accessible +4 state (TcO2), whereas Mn(IV) as MnO2 is common but strongly oxidizing. The expanded d-orbital participation in period-5 metals generally stabilizes higher oxidation states compared to period-4.
