Europium(II) iodide is the
iodide
An iodide ion is I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine deficiency ...
salt of divalent
europium
Europium is a chemical element; it has symbol Eu and atomic number 63. It is a silvery-white metal of the lanthanide series that reacts readily with air to form a dark oxide coating. Europium is the most chemically reactive, least dense, and soft ...
cation.
Preparation
Europium(II) iodide can be prepared in a handful of ways, including:
Reduction of
europium(III) iodide with
hydrogen
Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
gas at 350 °C:
:
Thermal decomposition of
europium(III) iodide at 200 °C:
:
Reaction of europium with
mercury(II) iodide
Mercury(II) iodide is a chemical compound with the molecular formula Hg I2. It is typically produced synthetically but can also be found in nature as the extremely rare mineral coccinite. Unlike the related mercury(II) chloride it is hardly solu ...
:
:
Reaction of europium with
ammonium iodide
Ammonium iodide is the inorganic compound with the formula NH4I. A white solid. It is an ionic compound, although impure samples appear yellow. This salt consists of ammonium cation and an iodide anion.Holleman, A. F.; Wiberg, E. ''Inorganic Chemis ...
:
:
Structure
Europium(II) iodide has several
polymorphs.
It adopts a
monoclinic
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...
crystal structure
In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...
in
space group P 21/c (no. 14).
It also adopts an
orthorhombic
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...
polymorph in
space group ''Pbca'' (no. 61). This form is
isostructural
Isostructural chemical compounds have similar chemical structures. " Isomorphous" when used in the relation to crystal structures is not synonymous: in addition to the same atomic connectivity that characterises isostructural compounds, isomorphous ...
with
strontium iodide.
A third polymorph of europium(II) iodide is formed if it is prepared from europium and ammonium iodide at low temperatures (200 K) in
liquid ammonia
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula . A stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pungent smell. It is widely used in fertilizers, ...
. This low-temperature phase is
orthorhombic
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...
and in
space group ''Pnma'' (no. 62). This is the same structure as modification IV of strontium iodide.
References
Europium(II) compounds
Iodides
Lanthanide halides
{{Inorganic-compound-stub