Technetium (Tc)

Silvery-gray metal

Technetium was the first artificially produced element and is used in millions of medical imaging scans yearly, and as the lightest radioactive element with no stable isotopes, technetium-99m (half-life 6 hours) emits gamma rays ideal for SPECT imaging. It is produced from molybdenum-99 decay in nuclear reactors.

Key metrics

Density11.5g/cm³

Melting point2,430K

Boiling point4,538K

Electronegativity1.9Pauling

Discovery

1937discovered

Discovered by: Emilio Segrè
Reactivity profile: Radioactive metal
Reactivity: Medium
Bonding: Metallic

Electron configuration

\textcolor{#6b7280}{[Kr]}\; \textcolor{#22c55e}{4_{d}^{5}}\; \textcolor{#ef4444}{5_{s}^{2}}

[Kr] 4d5 5s2

Wave function

\Psi_{\text{Tc}} \approx \frac{1}{\sqrt{43!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{43}(\mathbf{r}_{43}) \right|

Probability density $|\Psi|^2$ across the Tc valence shell.

Crystal structure

Hexagonal Close-Packed

Lattice constantsa 1.00 · b 1.00 · c 1.63

Cell anglesα 90° · β 90° · γ 120°

Coordination number12

Atoms per cell2

Atomic packing factor0.74

Physical properties

Atomic radius: 136 pm
Ionization energy: 702 kJ/mol
Electron affinity: 53 kJ/mol
Crystal structure: Hexagonal close-packed (hcp)

Oxidation states

+4+6+7

Acid/base

Can act as acid or base

Strongly acidicStrongly basic

State at 25 °CSolid

2430 K4538 K298 K

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

409.4nmTc I (violet)Violet60%

423.9nmTc IViolet80%

426.2nmTc I (blue)Violet100%

Dominant line 426.2 nmRange 409–426 nmTransitions 3