Lutetium (Lu)
Element 71 · Lanthanide · Solid at 25 °C · Period 6 (f-block)
Lutetium is the hardest and densest of the rare earths, and lutetium-based crystals detect the gamma rays in PET medical scanners.
On the periodic table, lutetium sits in the f-block in period 6. It is one of 15 elements classified as a lanthanide, and at room temperature (25 °C) it is a solid.
The lanthanides — often called rare-earth elements — fill the 4f orbitals along the detached row at the bottom of the table. Chemically they are remarkably alike, almost all preferring the +3 oxidation state, which historically made them very hard to separate. Today they are anything but obscure: strong permanent magnets, screen phosphors, and lasers depend on them.
Properties of lutetium
| Atomic number (Z) | 71 |
|---|---|
| Symbol | Lu |
| Atomic mass | 174.97 |
| Category | Lanthanide |
| Group | — (f-block, associated with group 3) |
| Period | 6 |
| Block | f-block |
| Metal / nonmetal | Metal |
| State at 25 °C | Solid |
| Electron configuration | [Xe] 4f14 5d1 6s2 |
| Electronegativity (Pauling) | 1.27 |
| Melting point | 1,652 °C (1,925.15 K / 3,005.6 °F) |
| Boiling point | 3,402 °C (3,675.15 K / 6,155.6 °F) |
| Density | 9.841 g/cm³ |
Position in the periodic table
Lutetium belongs to the lanthanides, the detached f-block row shown beneath the main table. These elements all fit between groups 2 and 4 of period 6, and are pulled out into their own row only to keep the table a manageable width.
Physical properties
Lutetium melts at 1,652 °C (1,925.15 K / 3,005.6 °F) and boils at 3,402 °C (3,675.15 K / 6,155.6 °F), giving it a liquid range of about 1,750 °C at standard pressure.
Its density is 9.841 g/cm³.
See also: the interactive periodic table, how to read the periodic table, periodic trends.