43 Tc

Technetium (Tc)

Element 43 · Transition metal · Solid at 25 °C · Group 7, Period 5

Technetium was the first element ever produced artificially. Its isotope technetium-99m is used in tens of millions of medical imaging scans every year.

On the periodic table, technetium sits in group 7 in period 5. It is one of 38 elements classified as a transition metal, and at room temperature (25 °C) it is a solid.

Transition metals occupy the wide d-block in the middle of the table. As a family they are hard, dense, high-melting metals that conduct heat and electricity well. Their partly filled d-orbitals let many of them take several oxidation states, form vividly colored compounds, and act as catalysts — which is why so much of industry, and so much of biology, runs on this block.

Properties of technetium

Properties of Technetium
Atomic number (Z)	43
Symbol	Tc
Atomic mass	(98) (mass number of the most stable isotope; this element has no standard atomic weight)
Category	Transition metal
Group	7
Period	5
Block	d-block
Metal / nonmetal	Metal
State at 25 °C	Solid
Electron configuration	[Kr] 4d5 5s2
Electronegativity (Pauling)	1.9
Melting point	2,157 °C (2,430.15 K / 3,914.6 °F)
Boiling point	4,265 °C (4,538.15 K / 7,709 °F)
Density	11 g/cm³

Position in the periodic table

Technetium shares group 7 with Manganese (Mn), Rhenium (Re), Bohrium (Bh). Elements in the same group have the same number of outer electrons, so they tend to behave alike chemically — comparing them is one of the fastest ways to see periodic trends in action.

Physical properties

Technetium melts at 2,157 °C (2,430.15 K / 3,914.6 °F) and boils at 4,265 °C (4,538.15 K / 7,709 °F), giving it a liquid range of about 2,108 °C at standard pressure.

Its density is 11 g/cm³.

Data notes

The atomic mass is shown in parentheses because this element has no standard atomic weight; the number given is the mass number of its most stable known isotope.