Yttrium – facts and properties
- Symbol
- Y
- Atomic number
- 39
- Atomic mass
- 88.906 u
- Period
- 5
- Group
- 3
- Category
- transition metal
- Electron configuration
- [Kr] 4d¹ 5s²
- Electronegativity
- 1.22
- Atomic radius
- 212 pm
- Valence electrons
- 3
- State at standard conditions
- solid
- Melting point
- 1522 °C
- Boiling point
- 3345 °C
- Density
- 4.47 g/cm³
- Discovered
- 1794
Yttrium is a silvery transition metal with atomic number 39. Chemically it belongs with the rare earths, and it carries the name of a Swedish village: Ytterby. A mineral from the quarry there led to the discovery of a new "earth" in 1794, from which yttrium could be won. The metal is hardly visible in daily life, yet it is widely used: its compounds glow red in fluorescent lamps, create the light of white LEDs and form laser crystals and superconductors.
Position in the periodic table
Occurrence and extraction
Yttrium never occurs as a free metal. In the Earth's crust it is more abundant than some familiar metals, but thinly spread. It is found as a companion in rare-earth minerals, for example xenotime, an yttrium phosphate, and monazite. Important sources also include clays in southern China from which rare earths can be leached.
A piece of history lies in the name. In 1787 an army officer found a heavy black mineral in a quarry at Ytterby near Stockholm. In 1794 the Finnish chemist Johan Gadolin examined it and found a new oxide "earth", later called yttria. Over time further elements were separated from yttria and its relatives. In all, four elements are named after Ytterby: yttrium, ytterbium, terbium and erbium.
The metal is obtained from yttrium compounds, for instance by reducing the fluoride with calcium. Separating it from the chemically very similar rare earths is laborious and takes many extraction steps. That makes pure yttrium comparatively expensive.
Properties and reactions
Yttrium is in period 5 and group 3, below scandium, and has the electron configuration [Kr] 4d¹ 5s². Its electronegativity is 1.22. The metal has a density of 4.47 g/cm³, melts at 1522 °C and boils at 3345 °C. It looks silvery and is softer than many transition metals. Chemically it behaves almost like a lanthanide, which is why it is counted among the rare earths.
In compounds yttrium occurs practically only with oxidation number plus three. In air the metal covers itself with a thin oxide layer that protects it, while powder and turnings ignite easily. With water and dilute acids it reacts like a base metal, releasing hydrogen, though only slowly in the cold.
The most important oxide is yttrium oxide, Y₂O₃, a white and very heat-resistant powder. It serves as a host lattice for other elements: add tiny amounts of other rare earths and the crystals glow in particular colours when they absorb energy. Yttrium resembles the lanthanides because its ionic radius is close to that of heavy ones such as holmium.
Uses in everyday life and technology
Yttrium becomes visible in light. In fluorescent lamps and formerly in tube screens, yttrium compounds doped with europium supplied the red. Today yttrium aluminium garnet, YAG for short, doped with cerium, sits in many white LEDs: a blue LED excites a yellow phosphor layer, and blue and yellow mix to white light. YAG is also a laser crystal. Doped with neodymium it forms the widespread Nd:YAG laser, used in materials processing, welding and medicine.
Its role in superconductivity is famous. In 1987 it was discovered that the ceramic YBCO, made of yttrium, barium, copper and oxygen, conducts current without resistance at temperatures above the boiling point of liquid nitrogen. That was a breakthrough, because liquid nitrogen is far cheaper than liquid helium. YBCO is used in magnets and cables but remains brittle and hard to process.
Yttrium oxide stabilises zirconium oxide. This ceramic is especially strong and heat-resistant. It serves as a thermal barrier coating on turbine blades, in dental restorations and in oxygen sensors such as the lambda sensor in a car.
In medicine the radioactive isotope yttrium-90 is used in cancer therapy, where tiny beads irradiate tumours in the liver directly. Yttrium has no known function in the body. Dust from yttrium compounds irritates the lungs, so it is handled only in specialist plants and not in school lessons.
Quick question
What is the atomic number of yttrium (Y)?
FAQ
Where does yttrium get its name?
From Ytterby in Sweden. A quarry there yielded a heavy black mineral. In it chemists found yttria, from which terbium, erbium and ytterbium were later separated. Four elements are therefore named after the same small village.
What is yttrium used for?
For phosphors that make the light of white LEDs and the red in fluorescent lamps, for laser crystals of yttrium aluminium garnet and for heat-resistant ceramics. It is also in the superconductor YBCO and in exhaust-gas sensors.
Is yttrium a rare earth?
Yes, it is counted as one, even though it is not a lanthanide. It sits in group 3 below scandium, yet behaves very much like the lanthanides and occurs in the same ores. The name "rare earths" is misleading: these elements are not especially rare, just hard to separate from one another.