71174.97LuLutetium
Lutetium (Lu) — element 71lanthanide · period 6
Lutetium is a chemical element with the symbol Lu and atomic number 71. It is a lanthanide in period 6 of the periodic table (the f-block), with a standard atomic mass of 174.97 u. At room temperature (25 °C) lutetium is a solid.
💡 Known for: The densest and hardest lanthanide; lutetium-177 is used in targeted cancer therapy.
# Lutetium properties
| Symbol | Lu |
|---|---|
| Atomic number | 71 |
| Atomic mass | 174.97 u |
| Category | lanthanide |
| Group | — (f-block, no group number) |
| Period | 6 |
| Block | f-block |
| Electron configuration | [Xe] 4f¹⁴ 5d¹ 6s² |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹ 6s² |
| Electrons per shell | 2, 8, 18, 32, 9, 2 |
| Protons / electrons | 71 / 71 |
| State at 25 °C | solid |
| Melting point | 1925 K (1651.8 °C, 3005.3 °F) |
| Boiling point | 3675 K (3401.8 °C, 6155.3 °F) |
| Density | 9.841 g/cm³ |
| Electronegativity (Pauling) | 1.27 |
| First ionization energy | 5.426 eV |
| Atomic radius | 217 pm |
| Discovered | 1907 |
# Electron configuration of lutetium
The electron configuration of lutetium is [Xe] 4f¹⁴ 5d¹ 6s², written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹ 6s². Its 71 electrons fill 6 shells as 2, 8, 18, 32, 9, 2, so the outermost shell holds 2 electrons.
# Related elements
YbYtterbiumprevious elementHfHafniumnext elementLaLanthanumlanthanideCeCeriumlanthanidePrPraseodymiumlanthanideNdNeodymiumlanthanidePmPromethiumlanthanideSmSamariumlanthanideEuEuropiumlanthanideGdGadoliniumlanthanide
# Lutetium FAQ
What is the atomic number of lutetium?
The atomic number of lutetium is 71: every lutetium atom has 71 protons in its nucleus. Its symbol is Lu.
What is the atomic mass of lutetium?
The standard atomic mass of lutetium is 174.97 u.
What is the electron configuration of lutetium?
Lutetium's electron configuration is [Xe] 4f¹⁴ 5d¹ 6s² (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹ 6s²), with 2, 8, 18, 32, 9, 2 electrons per shell.
Is lutetium a metal?
Yes. Lutetium is a lanthanide, one of the metals.
What is the melting point of lutetium?
Lutetium melts at 1925 K (1651.8 °C, 3005.3 °F) and boils at 3675 K (3401.8 °C, 6155.3 °F).
What is lutetium used for / known for?
The densest and hardest lanthanide; lutetium-177 is used in targeted cancer therapy.