Atomic Properties of Lu
- Atomic Number of Lu
- 71
- Atomic Mass of Lu
- 174.9700 u
- Electron Configuration
- [Xe] 4f14 5d1 6s2
- Electronegativity
- 1.27
- Block
- d-block
- Group
- —
- Period
- 6
In 1907, Georges Urbain separated a new component from ytterbium and named it lutecium for Lutetia, the Roman name of Paris; the spelling later became lutetium. Carl Auer von Welsbach independently reported the element and proposed cassiopeium, a name used in some countries for years. The dispute reflected how difficult it was to prove a final separation among nearly identical rare earths.
Lutetium is commonly placed at the far end of the lanthanide row. It is one of the densest lanthanides, giving the phrase small, heavy reminder a physical basis. Its filled 4f shell and relatively small ionic radius help distinguish its chemistry from earlier members.
In medical imaging, lutetium-containing scintillator crystals such as LYSO convert incoming high-energy radiation into flashes that detectors can count in PET scanners. The crystal contains lutetium; a lutetium isotope is not simply injected to make a PET picture. In a separate application, lutetium-177 is attached to targeting molecules for radiopharmaceutical therapies that deliver beta radiation to selected tumor cells under clinical control.
Natural lutetium is mostly stable lutetium-175 with a small amount of long-lived lutetium-176. Decay of lutetium-176 to hafnium-176 provides a clock for dating ancient rocks and planetary materials.
This Luminary closes the series with precision across scales. A crystal times a detector flash, a targeted isotope deposits radiation in tissue, and an extremely slow decay records geological history. The final square is less an ending than three exact ways to measure change.