Ytterbium (Yb)
“The element that fills the 4f sub-shell’s very last slot — and runs the world’s most precise clocks and mightiest fibre lasers.”
How its electrons are arranged
Computed from the aufbau principle, with known real-world exceptions applied automatically.
Characteristics
- Electron configuration [Xe] 4f¹⁴ 6s² — the 4f sub-shell is completely full, the crowning moment of the f-block’s filling story just before lutetium closes the row.
- Unusually for a lanthanide it lives in two oxidation states: Yb³⁺ ([Xe] 4f¹³) and Yb²⁺, whose completely filled 4f¹⁴ shell makes it a rare closed-shell ion — chemistry that echoes europium’s Eu²⁺.
- A soft, quick-tarnishing metal with a strikingly low melting point for a lanthanide (824 °C) — it melts long before its neighbours even warm up.
- Its atoms keep time like nothing else: ytterbium-171 optical lattice clocks are so steady they would not lose or gain a second over the age of the universe.
A soft, bright-silvery metal — strikingly low-melting for a lanthanide, at 824 °C — that tarnishes quickly in air and reacts steadily with water. Its Yb³⁺ salts are colourless, while its rarer Yb²⁺ compounds wear a soft green.
Where you meet it
✦ Uses
- Ytterbium-171 optical lattice clocks — the world’s most precise timekeepers and frontrunners for a new definition of the second.
- Yb:YAG disc lasers and ytterbium-doped fibre lasers — the industrial workhorses that robot-weld car bodies and cut steel sheet at kilowatt power.
- Ytterbium-169 gamma sources for compact radiotherapy units and on-site industrial radiography.
- Stress gauges that watch rock strain in earthquake studies, and grain-refining additives in special stainless steels.
◍ Everyday examples
- The national timekeeping laboratories of the United States, Europe and Asia now run ytterbium lattice clocks as candidates for the coming redefinition of the second.
- Many a car body rolled out by a robotic factory line was welded together by the beam of a ytterbium-doped fibre laser.
History & name
In 1878 the Swiss chemist Jean Charles Galissard de Marignac, poring over erbium oxide in Geneva, detected a new earth he named ytterbia — after Ytterby, the Swedish quarry village already famous in element names. But his “new element” still hid a secret: in 1907 Georges Urbain in Paris, Carl Auer von Welsbach in Vienna and Charles James in America independently split ytterbia in two, yielding element 70 and element 71. After a fierce naming dispute settled in Urbain’s favour, element 70 kept the name ytterbium while its twin became lutetium — the closing chapter of the little village that named four elements.