What Is Lutetium?

Lutetium, atomic number 71 and symbol Lu, belongs to the lanthanides — the row of rare earth elements beneath the main periodic table.

The last of the lanthanide series. Named after Lutetia (Paris in Latin).

As a lanthanide in Period 6 and Group 3 (Transition Metals), lutetium's placement on the table reflects its electron configuration of [Xe] 4f¹⁴ 5d¹ 6s², which governs its bonding behavior and the type of compounds it typically forms.

Position on the Periodic Table

Lutetium is located in Period 6, an unusually long row that includes the entire lanthanide series.

Within that row, lutetium sits in Group 3 (Transition Metals), alongside elements that share a similar number of valence electrons and, by extension, similar chemical behavior.

This position is not arbitrary — the periodic table was deliberately organized so that an element's row and column reveal its expected reactivity, bonding pattern, and physical state at a glance.

Physical & Chemical Properties

Lutetium has an atomic mass of 174.967 u and a density of 9.84 g/cm³. Its melting point is 1663°C and its boiling point is 3402°C.

Lutetium displays the typical lanthanide combination of a silvery appearance and chemistry dominated by its f-orbital electrons.

Electron Configuration Explained

Lutetium's electron configuration is [Xe] 4f¹⁴ 5d¹ 6s², describing how its electrons are distributed across shells and subshells around the nucleus.

Reading the configuration in order shows electrons filling shells of increasing energy, following the standard Aufbau principle that explains how atomic structure builds up across the periodic table.

The outermost (valence) electrons shown in this configuration are what ultimately determine lutetium's chemical reactivity and the type of bonds it forms with other elements.

History & Discovery

Lutetium was formally discovered in 1907, G. Urbain, identified through the careful isolation and analytical techniques typical of that era's chemical research.

Many elements from this period were anticipated by Dmitri Mendeleev's periodic table, which successfully predicted gaps corresponding to undiscovered elements well before laboratory instruments existed to confirm them directly.

What Is Lutetium Used For?

Lutetium's specific properties make it useful in several applications, including:

  • PET scan detectors
  • Catalysts
  • Alloys
  • Lutetium-177 cancer therapy
  • Research

These uses reflect lutetium's underlying classification as a lanthanide, since the same properties that define its category in chemistry also determine where it becomes practically useful.

Fun Facts About Lutetium

  • Lutetium-177 delivers radiation directly to tumor cells for targeted cancer therapy.
  • Lutetium is element number 71 on the periodic table, in Period 6 and Group 3.
  • Its standard atomic mass is 174.967 u, calculated from the natural abundance of its isotopes.

Frequently Asked Questions

What is Lutetium's atomic number?
Lutetium has atomic number 71.

What is Lutetium's chemical symbol?
Lutetium's symbol is Lu.

What group and period is Lutetium in?
Lutetium is in Period 6, Group 3 (Transition Metals).

What is Lutetium's atomic mass?
Lutetium's standard atomic mass is 174.967 u.