Atomic number 70

Ytterbium

Yb
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− phase

Shells Orbitals 4f 6s

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70 electrons in 6 shells: 2, 8, 18, 32, 8, 2.

Shells are a teaching model: an electron does not travel on a ring at a fixed distance.

Category: Lanthanide
Period: 6
Block: f
Standard atomic weight: 173.05(2) Da
Electron configuration: [Xe] 4f¹⁴ 6s²
Phase at 25 °C: solid
Melting point: 819 °C
Boiling point: 1196 °C
Density: 6.90 g/cm³
Discovered: 1878, Jean Charles Galissard de Marignac

Neighbours in the table

Tm Lu

Working in 1878, Jean Charles Galissard de Marignac of Switzerland pulled a new component out of erbia and named it ytterbia, in Los Alamos’s and Jefferson Lab’s accounts. Erbia was then an “earth” in the chemists’ sense, a material holding elements not yet isolated. He took it for a compound of one new element, ytterbium. Georges Urbain, a French chemist, suspected a mixture instead. In 1907 he split ytterbia into neoytterbia and lutecia, whose elements are now called ytterbium and lutetium. Von Welsbach reached the same pair independently at about the same time and named them aldebaranium and cassiopeium.

A full 4f subshell of fourteen marks ytterbium’s configuration, [Xe] 4f¹⁴ 6s², which sets 70 electrons in shells of 2, 8, 18, 32, 8 and 2. The metal is soft, malleable and quite ductile, with a bright silvery lustre. In a metal each ion sits in a fluid of electrons on every side, in Stephen Lower’s Chem1 account, and that bonding without direction accounts for the ductility.

Ytterbium has three allotropes, or crystal forms, with changes at −13 °C and 795 °C. The beta form, stable at room temperature, is face-centred cubic, with atoms at the corners of a cube and the centre of each face. The high-temperature gamma form is body-centred cubic, with one atom at the cube’s centre instead.

Where it is found

Ytterby, a village in Sweden, gave ytterbium its name. The mineral ytterbite was first found there, according to CIAAW, the atomic-weights commission of IUPAC (the International Union of Pure and Applied Chemistry). That mineral, now called gadolinite, was the source of Marignac’s erbium nitrate. The same village also named yttrium, erbium and terbium, Los Alamos notes.

An estimated 3.2 milligrams of ytterbium sit in each kilogram of the Earth’s crust, and seawater carries 8.2 × 10⁻⁷ milligrams per litre, in Jefferson Lab’s figures. Several rare minerals hold it alongside other rare earths. Monazite sand, with about 0.03 per cent ytterbium, is its main commercial source, and ion exchange separates it out.

Natural ytterbium is a blend of seven stable isotopes. Ytterbium-174 is the commonest at 31.896 per cent, in CIAAW’s figures, and ytterbium-168 the scarcest at 0.126 per cent. Klemm and Bonner first prepared the metal in 1937 from ytterbium trichloride and potassium, but their product was mixed with potassium chloride. In 1953 Daane, Dennison and Spedding made a far purer sample, pure enough to measure the element’s properties.

Why it matters

Pressure changes how the beta form carries current. It normally conducts like a metal, yet at about 16,000 atmospheres it becomes a semiconductor, Los Alamos reports. Its electrical resistance climbs tenfold by 39,000 atmospheres. At 40,000 atmospheres it falls to about a tenth of its value at ordinary temperature and pressure.

Ytterbium-169 works outside the laboratory. Neutron capture turns ytterbium-168 into it, and it emits gamma rays, in IUPAC’s isotope notes. Without electricity, it can form a radiographic image, a picture on film of rays passing through an object. Such images reveal flaws in castings and welds. Gamma cameras that find sealed sources and hot spots in old waste use it as a radiation source.

Its half-life, the time for half a sample to decay, is 32.018 days in the evaluation of the International Atomic Energy Agency (IAEA). For prostate cancer seed implants, ytterbium-169 has been suggested as an alternative to iodine-125 and palladium-103.

Another isotope, ytterbium-171, has been used to build an atomic clock on an optical lattice, a pattern formed where laser beams travelling in opposite directions interfere. Alloyed with stainless steel, ytterbium might improve its strength and other mechanical properties, Los Alamos suggests. It is added to fibre-optic cable as a doping agent, a small deliberate addition to the glass, where it can act as an amplifier.

Properties

Properties of ytterbium Standard atomic weights from IUPAC/CIAAW (abridged, 2024); other values from PubChem's periodic table, kelvin converted to °C.
Property	Value	Unit	Source
Atomic number	70
Standard atomic weight	173.05(2) Da	Da	IUPAC/CIAAW 2024
Melting point	819 °C	°C	Los Alamos: 819 °C
Boiling point	1196 °C	°C	Los Alamos: 1196 °C
Density	6.90 g/cm³	g/cm³
Electron configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴
Phase at 25 °C	solid

Safety

Ytterbium metal is classed as a flammable solid in 84% of the company reports behind its hazard classification, under the signal word Danger of the Globally Harmonized System (GHS). The same share call it harmful if swallowed, if inhaled or in contact with skin, and 82% add skin, eye and respiratory irritation. Its acute toxicity rating is low, according to Haz-Map and Los Alamos. For anyone handling the metal, the handling precautions are in the PubChem Laboratory Chemical Safety Summary for ytterbium.

Questions

Where does the name ytterbium come from?

The name goes back to Ytterby, a Swedish village, by way of the materials chemists pulled from its minerals, called earths, which held elements not yet isolated. In 1843 Carl Gustaf Mosander split gadolinite into yttria, erbia and terbia, in Jefferson Lab's history on PubChem's record. By 1877 the names erbia and terbia had been swapped. Marignac then drew ytterbia out of erbia, and ytterbium kept the village's name.

Is ytterbium radioactive?

Natural ytterbium is not: it is a mixture of seven stable isotopes, according to Los Alamos. Radioactive ytterbium-169 is made by neutron capture in ytterbium-168 and emits gamma rays, in IUPAC's isotope notes; its half-life is 32.018 days in the evaluation of the International Atomic Energy Agency (IAEA). That gamma emission is what lets it serve as a portable radiography source for checking castings and welds.

Does ytterbium react with water?

Slowly. Ytterbium is fairly stable, Los Alamos notes, yet it reacts slowly with water and is readily attacked and dissolved by mineral acids, dilute or concentrated. It is also soft, malleable and quite ductile. Ytterbium has a bright silvery lustre, according to Los Alamos.

Who really discovered ytterbium?

Marignac keeps the credit for 1878, even though his ytterbia later proved to hold two elements. He is credited because of his original view of what ytterbia contained, Jefferson Lab explains. After Georges Urbain split it in 1907, neoytterbium reverted to the name ytterbium, and chemists respelled lutecium as lutetium.