The Techy Element Technetium

Introduction to Technetium

The element Technetium is a silvery gray transition metal. It has the atomic number of 43 and has the atomic symbol Tc. It is also the lightest element with all radioactive isotopes and the first artificially produced element.

10 Fun Facts about Technetium

The name “technetium’ derives from the Greek word “technetos,” which means “artificial.” This is because it’s the first artificially produced element.
The longest-living isotope of Tc has a relatively short half-life of 4.21 million years.
Although the natural occurrence of Tc on Earth is rare, Scientists detected it in red giants in 1952
It is the lightest element with isotopes that are all radioactive
Medical professionals use Technetium-99m for medical imaging because of its gamma-ray emittance and its short half-life of 6.01 hours
Technetium can exist in oxidation states ranging from -3 to +7, with the +7 and +4 oxidation states being the most stable.
It has a relatively high melting point of 2204 degrees Celcius and a boiling point of 4265 degrees Celcius.
It is a very good corrosion inhibitor for steel
Over 50 radiopharmaceuticals are based on technetium-99m
It is a fission product in nuclear reactors.

Technetium in the Periodic Table

Technetium has the atomic symbol Tc with an atomic number of 43, in the d-block of the periodic table, with molybdenum to its left and ruthenium to its right. It is a transition metal in group 7 and period 5 of the periodic table. Tc has an electron configuration of [Kr] 4d⁵ 5s², with 7 valence electrons. It is the lightest element without a stable isotope. Additionally, the element has an electronegativity of 1.9 on the Pauling scale.

Technetium Applications in Today’s World

What is it used for?

Technetium-99m emits gamma rays, serving as a good radioactive tracer used for medical diagnostic studies and tests. It’s also suited for this role because of its short half-life of 6.01 hours. Radiopharmaceuticals based on technetium-99m are used for studies of the brain, heart muscle, lungs, blood, tumors, etc.

This element is also an effective corrosion inhibitor for steel, but this use is limited to closed systems because of its radioactivity. Because of its radioactivity, the use of this element for corrosion protection is usually impractical.

Technetium-99 emits beta particles with low energies and no gamma rays. Also, its long half-life causes its emission rate to decrease very slowly. Therefore, the National Institute of Standards and Technology uses it as a standard beta emitter for equipment calibration.

Tc can also serve as an effective catalyst in processes like the dehydrogenation of isopropyl alcohol. However, radioactivity is a major obstacle in these reactions.

Where is it Found?

This element appears only in tiny traces in the earth’s crust because of its short half-life of only 4.21 million years. It also appears in minuscule amounts in uranium ore since it is a product of uranium fission.

When and How Was Technetium Discovered?

In 1925, German chemists reported the discovery of element 43, but since other scientists couldn’t replicate the discovery, they dismissed it as an error. The discovery of element 43 was confirmed in 1937 at the University of Palermo in Sicily by Carlo Perrier and Emilio Segrè. They isolated it from a molybdenum strip from California by bombarding molybdenum atoms with deuterons that a cyclotron device had accelerated.

Technetium Chemistry (Compounds, Reactions, Oxidation States)

Pertechnetate

Lewis structure of a pertechnetate ion (TcO₄⁻). Source.

Pertechnetate (TcO₄⁻) is mostly produced by the radioactive decay of [⁹⁹MoO₄]²⁻.

$\begin{gather*} [^{99}MoO_{4}]^{2-} \longrightarrow [^{99m}{Tc} O_{4}]^{-} + e^{-1} \end{gather*}$

Related to pertechnetate is technetium heptoxide, a volatile solid formed by the oxidation of technetium.

$\begin{gather*} 4Tc + 7 O_2 \longrightarrow 2Tc_2O_7 \end{gather*}$

Technetium heptoxide hydrolyzes to form pertechnetate. This hydrolysis also forms pertechnetic acid (HTcO₄), a strong acid. Whether this hydrolysis forms pertechnetate or pertechnetic acid depends on the pH.

$\begin{gather*} 2Tc_2O_7 + 2OH^- \longrightarrow 2TcO_4^- + H_2O \end{gather*}$

$\begin{gather*} 2Tc_2O_7 + H_2O \longrightarrow 2HTcO_4 \end{gather*}$

The most common and easily accessible form of technetium is sodium pertechnetate Na[TcO₄]. However, there are still other compounds like potassium pertechnetate K[TcO₄] and lithium pertechnetate Li[TcO₄].

Halides

TcF₆, TcF₅, TcCl₄, TcBr₄, TcBr₃, α-TcCl₃, β-TcCl₃, TcI₃, α-TcCl₂, and β-TcCl₂

The oxidation states vary from +4 to +2. They also have differing structures, including molecular octahedral complexes, extended chains, layered sheets, etc. For example, the structure of TcCl₄ is composed of zigzag chains of edge-sharing TcCl₆ octahedral complexes. TcCl₄ is isomorphous (has a similar structure) to other metal tetrachlorides like ZrCl₄, whose structure is shown below.

Structure of zirconium tetrachloride ZrCl₄, which has a similar structure to technetium tetrachloride TcCl₄. It has a chain-like structure of edge-sharing metal hexachloride octahedral complexes. Source.

Technetium tetrachloride is formed by the reaction of Cl₂ with Tc metal at high temperatures between 300 and 500 °C:

$\begin{gather*} Tc + 2Cl_2 \longrightarrow TcCl_4 \end{gather*}$

Chalcogenide

Technetium-

dioxide: TcO₂

disulfide: TcS₂

diselenide: TcSe₂

ditelluride: TcTe₂

Other:

Hydride: TcH₉²⁻

Technetium Oxidation States

The element has a diverse range of oxidation states, including -3, -1, +1, +2, +3, +4, +5, +6, and +7. The most common oxidation states are +7, +4, and +5.

Physical Properties of Technetium

Technetium Symbol: Tc
Melting point: 2157°c
Boiling point: 4265°c
Density: 11 g/cm³
Atomic weight: 98.9062 g/mol
Atomic number: 43
Electronegativity: 1.9
Classification: Group 7 Metal
Electron shell configuration: [Kr] 4d5 5s2
Isotopes – Technetium has 22 reported isotopes, all are radioactive
Found as a spontaneous fission product in uranium ore and thorium ore, Primarily man-made
Toxicity: Can pose a health risk when in the human body. It is radioactive, so there are effects that come with radiation

Where can I buy Technetium?

Because of its radioactivity and potential use in nuclear weapons, the sale of technetium is strictly regulated.