Ytterbium

Ytterbium,  ₇₀Yb

A piece of ytterbium metal
General properties
Name, symbol	Ytterbium, Yb
Appearance	Metallic cream
Ytterbium in the periodic table
- ↑ Yb ↓ No Thulium ← Ytterbium → Lutetium
Atomic number	70
Standard atomic weight (Ar)	173.045(10)
Group, block	, f-block
Period	period 6
Electron configuration	[Xe] 4f14 6s2
per shell	2, 8, 18, 32, 8, 2
Physical properties
Silvery-white
Phase	Solid
Melting point	1097 K ​(824 °C, ​1515 °F)
Boiling point	1469 K ​(1196 °C, ​​2185 °F)
Density near r.t.	6.90 g/cm3
when liquid, at	6.21 g/cm3
Heat of fusion	7.66 kJ/mol
Heat of	129 kJ/mol
Molar heat capacity	26.74 J/(mol·K)
pressure
Atomic properties
Oxidation states	3, 2, 1 ​(a basic oxide)
Electronegativity	Pauling scale: 1.1
energies	1st: 603.4 kJ/mol 2nd: 1174.8 kJ/mol 3rd: 2417 kJ/mol
Atomic radius	empirical: 176 pm
Covalent radius	187±8 pm
Miscellanea
Crystal structure	​Face-centered cubic (fcc)
Speed of sound thin rod	1590 m/s (at 20 °C)
Thermal expansion	26.3 µm/(m·K) (β, poly)
Thermal conductivity	38.5 W/(m·K)
Electrical resistivity	2.5·-7 Ω·m (β, poly)
Magnetic ordering	Paramagnetic
Young's modulus	23.9 GPa (β form)
Shear modulus	9.9 GPa (β form)
Bulk modulus	30.5 GPa (β form)
Poisson ratio	0.207 (β form)
Vickers hardness	205–250 MPa
Brinell hardness	340–440 MPa
CAS Registry Number	7440-64-4
History
Naming	After Ytterby (Sweden), where it was mined
Discovery	Jean Charles Galissard de Marignac (1878)
First isolation	Carl Auer von Welsbach (1906)

Ytterbium is a lanthanide with the symbol Yb and atomic number 70. It is a hard, silvery metal, sometimes described as slightly brassy, that is about as reactive as magnesium. It is not a particularly interesting addition to the amateur chemist's lab, but it and its ytterbium(II) derivatives are powerful reducing agents that can be used in organic synthesis as an alternative to samarium and its samarium(II) derivatives.

Properties

Physical properties

Ytterbium is a slightly brassy metal, sometimes found darkened as it slowly tarnishes in air over the course of months or years. It exists in three allotropes: α-ytterbium, which exists in a hexagonal crystal structure is stable below -13 °C and is diamagnetic, β-ytterbium, which is stable at room temperature, paramagnetic and exists in a face-centered cubic structure, and γ-ytterbium, which exists above 795 °C and has a body centered cubic structure.

Ytterbium can be thought of as analogous to zinc in terms of its relation to the other lanthanides. Due to the filled f-shell, the metal has an unusually low melting and boiling point (824 °C and 1196 °C respectively), and is also less dense than most other lanthanides. Melting ytterbium (which must be done in an inert atmosphere to prevent ignition of the metal) will invariably cause some to boil off due to the narrow liquid range. This filled f-shell contributes to ytterbium's extremely low magnetism compared to rare earths such as gadolinium, terbium and dysprosium. However, fine ytterbium powder can be picked up by a neodymium magnet.

Ytterbium is also notoriously soft and sticky. Although filing ytterbium into powder is easier than it is for other lanthanides, it will leave traces of itself behind in the grooves of the file, and it is nearly impossible to remove once situated there. It is best to dedicate a file to ytterbium and use a different file for other elements to limit contamination.

Chemical properties

Ytterbium is a reactive metal, but it does not tarnish quickly in air, taking months or years to do so, and unless stored with complete disregard for its properties, rarely corrodes to the oxide. It does, however, burn in air to form ytterbium(III) oxide. Ytterbium powder burns with a characteristic green flame, notably in compositions with hexachloroethane and PTFE.

Ytterbium reacts vigorously with dilute acids to form salts. Most of these salts are soluble in water except for the fluoride and oxalate. All of these salts are white in color. Ytterbium also reacts with the halogens to form trihalides. The metal reacts only slowly in cold water, but vigorously in hot water, to form ytterbium hydroxide, which is basic enough to absorb carbon dioxide from the air to form ytterbium carbonate.

Under reducing conditions, ytterbium(II) species is known to exist. This ion will reduce water to hydrogen gas and is therefore unstable in aqueous solution, but it is present long enough to be detected. It can be isolated in tetrahydrofuran. Ytterbium(II) compounds can be formed by reacting metallic ytterbium with ytterbium(III) compounds, but they disproportionate back to ytterbium metal and ytterbium(III) compounds at elevated temperatures.

In glacial acetic acid, ytterbium dissolves slowly and forms an orange solution, likely an ytterbium(II) acetato complex. Adding water considerably increases the rate of reaction and limits the formation of the orange species. The resulting ytterbium(III) acetate tetrahydrate forms large rhombic crystals after slow evaporation.

Availability

Ytterbium is more common than iodine on Earth, but it is very hard to find and relatively expensive. One source for ytterbium, as well as other rare earth metals, is Metallium. It is sold in 5 gram and 20 gram sizes, as well as rods, ampoules, and coins. Ytterbium and its compounds are occasionally sold on eBay as well.

Projects

• Making and using ytterbium(II) compounds
• Green-burning energetic mixtures

Handling

Safety

Toxicity

Ytterbium compounds have not been investigated for their toxicity, and should be treated as mildly toxic. Ytterbium has no biological role but may stimulate metabolism. Salts of ytterbium, especially the halides, tend to hydrolyze at elevated temperatures and may emit noxious or strongly acidic vapors (commonly HCl in the case of ytterbium(III) chloride).

Flammability

Ytterbium as small pieces will ignite in the presence of an open flame, and ytterbium dust and powder may ignite very easily. Ytterbium and thulium fires may be identified by their brilliant green flames. Class D fire extinguishers should be at hand. Water may aggravate burning ytterbium and should never be used to put out the flame.

Storage

Ytterbium should be stored in closed containers, away from any acids and oxidizing agents, particularly volatile ones. It is stable in air almost indefinitely, but does tarnish slowly.

Disposal

Best to try to recycle it.

References

Relevant Sciencemadness threads

None as of yet - why not start some research on this element?