Discovered | Name | Prepared | Characteristics | Uses

Technetium is a transition metal in Group VIIB (Group 7) and the 5th period. Other members of the group are manganese (Mn) and rhenium (Re).

The element was first detected in 1937 by C. Perrier and E. Segrè in a sample of molybdenum that had been bombarded with deuterons in a cyclotron in California.

Mo + D Tc

It was the first element to be produced artificially and so was named technetium from the Greek word for artificial. Nineteen isotopes, with mass numbers from 90 to 108, are known, but the principal isotopes are 93, and 95-99. All are radioactive. For example, 99Tc in a beta emitter with a half life of 213,000 years.

The element is produced by reducing Tc2S7 with H2 gas at 1100°C.

Tc2S7 + 14 H2 7 H2S + 2 Tc

In other transition metal groups the two heavier elements are similar in their chemistry but somewhat different than the lightest element. This is the case here, as Tc has a chemistry similar to that of rhenium.

Although technetium is produced artificially, its chemistry has been extensively studied. It has oxidation numbers ranging from 0 to +7, with 0, +2, +4, +5, +6, and +7 most common.

The elements of Group VIIB have many contrasting features. Metallic manganese was isolated in 1774, but its compounds have been known and used for centuries. Rhenium also occurs naturally, but only in trace amounts; its estimated terrestrial abundance is only 0.0007 ppm, similar to that of the platinum group metals. On the other hand, technetium is man-made, albeit in kilogram quantities.

The principal use of the element is as sodium pertechnetate (NaTcO4) in clinical nuclear medicine. Indeed, metastable 99Tc (half life 6.0 hours, gamma emitter) is the principal isotope used in this field of medicine. For example, it is used in imaging studies of the brain, bones, and liver and in determining blood volume.

It is a remarkable corrosion inhibitor for steel. A trace of KTcO4 will protect steel up to temperatures of 250°C. However, as Tc is radioactive, this is suitable only in a closed environment.