Chemical element · reference page

71Lu

Lutetium

Lutetium is element 71 (Lu), located in period 6, group 3 and the d block. At room temperature its reference phase is solid. Its electron configuration is [Xe] 4f14 5d1 6s2.

Atomic number71

Standard atomic weight174.96669(5)

Group3

Period6

Blockd

Electron configuration[Xe] 4f14 5d1 6s2

Electronic structure

What controls its chemistry

The d subshell participates in the chemistry of lutetium. Transition metals can use electrons of similar energies in bonding, which is why variable oxidation states, coordination compounds and catalytic behaviour are common across the d block.

Its electron configuration, [Xe] 4f14 5d1 6s2, should be read together with the oxidation state of the compound: removing electrons changes which d orbitals are occupied and can alter colour, magnetism, bonding and reactivity.

Chemical forms

Compounds, ions and materials

For lutetium, important chemical forms include metals and alloys, oxides, halides and coordination compounds. Variable oxidation states are common because s and d electrons have similar energies, and ligands around the metal ion can strongly alter colour, magnetism and reactivity.

Physical behaviour

State and phase changes

The reference phase at room temperature is solid. The listed density is 9.841 g/cm³. The melting point is 1 950 K (1 677 °C). The boiling point is 3 675 K (3 402 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where lutetium is found and used

In practice, lutetium is encountered in catalysts, medical imaging equipment and scientific research.

In practice

Examples of real uses

Catalysts

Lutetium is used to accelerate chemical reactions without being consumed in the overall reaction.

Medical imaging equipment

Lutetium is used in imaging agents, detector materials or the high-field magnets and specialised components of imaging systems.

Scientific research

Lutetium is produced, isolated or measured mainly to test atomic, nuclear and periodic trends rather than for bulk commercial use.

Periodic position

What its neighbours tell us

Lutetium is in period 6. In the f-block sequence shown here, it appears between ytterbium and hafnium. This sequence allows a direct comparison with the neighbouring f-block elements.

Reference data

Physical and atomic properties

Classificationlanthanide

Phase at room temperatureSolid

Electron shells2 · 8 · 18 · 32 · 9 · 2

Density9.841 g/cm³

Melting point1 950 K (1 677 °C)

Boiling point3 675 K (3 402 °C)

Pauling electronegativity1.27

First ionisation energy523.5 kJ/mol

Electron affinity33.4 kJ/mol

Values describe the element or neutral atom where applicable. Physical data can depend on allotrope, pressure and measurement conditions.

History

Discovery and identification

The discovery of lutetium is associated with Georges Urbain. Recognition of the element, isolation of a pure sample and assignment of its modern atomic number did not necessarily occur at the same time.

Isotopes and atomic weight

How isotope composition changes the numbers

The standard atomic weight is 174.96669(5). This value refers to the isotopic composition of natural terrestrial material, not to the mass of one specific atom.

Lutetium has at least one stable isotope. Different isotopes have the same number of protons and therefore the same element identity, but different neutron numbers and atomic masses.

Safety

Handling and exposure

The hazards associated with lutetium depend on chemical form, dose and route of exposure. Pure lutetium, its ions and its compounds can have very different biological and environmental effects, so safety data should be checked for the actual substance being handled.