Beryllia

Beryllium oxide

Names
Preferred IUPAC name Beryllium(II) monoxide
Systematic IUPAC name Oxoberyllium
Other names Beryllia, Thermalox, Natural bromellite, Thermalox 995.
Identifiers
CAS Number	1304-56-9 Y
3D model (Jmol)	Interactive image Interactive image
Beilstein Reference	3902801
ChEBI	CHEBI:62842 N
ChemSpider	14092 Y
ECHA InfoCard	100.013.758
EC Number	215-133-1
MeSH	beryllium+oxide
PubChem	14775
RTECS number	DS4025000
UN number	1566
InChI InChI=1S/Be.O Y Key: LTPBRCUWZOMYOC-UHFFFAOYSA-N Y InChI=1/Be.O/rBeO/c1-2 Key: LTPBRCUWZOMYOC-SRAGPBHZAE
SMILES [Be]=[O] [Be-]#[O+]
Properties
Chemical formula	BeO
Molar mass	25.01 g·mol−1
Appearance	Colourless, vitreous crystals
Odor	Odourless
Density	3.01 g cm−3
Melting point	2,507 °C (4,545 °F; 2,780 K)
Boiling point	3,900 °C (7,050 °F; 4,170 K)
Solubility in water	0.00002 g/100 mL
Band gap	10.6 eV
Thermal conductivity	330 W K−1 m−1
Refractive index (nD)	1.719
Structure
Crystal structure	Hexagonal
Space group	P63mc
Point group	C6v
Coordination geometry	Tetragonal
Molecular shape	Linear
Thermochemistry
Specific heat capacity (C)	25.5 J/mol K
Std molar entropy (So298)	13.73–13.81 J K−1 mol−1
Std enthalpy of formation (ΔfHo298)	−599 kJ/mol
Gibbs free energy (ΔfG˚)	−582 kJ/mol
Hazards
Safety data sheet	See: data page
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H301, H315, H317, H319, H330, H335, H350, H372
GHS precautionary statements	P201, P260, P280, P284, P301+310, P305+351+338
EU classification (DSD)	T+
R-phrases	R49, R25, R26, R36/37/38, R43, R48/23
S-phrases	S53, S45
NFPA 704	0 4 0
Lethal dose or concentration (LD, LC):
LD50 (median dose)	2062 mg kg−1 (mouse, oral)
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 0.002 mg/m3 C 0.005 mg/m3 (30 minutes), with a maximum peak of 0.025 mg/m3 (as Be)
REL (Recommended)	Ca C 0.0005 mg/m3 (as Be)
IDLH (Immediate danger)	Ca [4 mg/m3 (as Be)]
Related compounds
Other anions	Beryllium telluride
Other cations	Magnesium oxide Calcium oxide
Supplementary data page
Structure and properties	Refractive index (n), Dielectric constant (εr), etc.
Thermodynamic data	Phase behaviour solid–liquid–gas
Spectral data	UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Beryllium oxide (BeO), also known as beryllia, is an inorganic compound with the formula BeO. This colourless solid is a notable electrical insulator with a higher thermal conductivity than any other non-metal except diamond, and exceeds that of most metals. As an amorphous solid, beryllium oxide is white. Its high melting point leads to its use as a refractory. It occurs in nature as the mineral bromellite. Historically and in materials science, beryllium oxide was called glucina or glucinium oxide. Formation of BeO from beryllium and oxygen releases the highest energy per mass of reactants for any chemical reaction, close to 24 MJ/kg.

Beryllium oxide can be prepared by calcining (roasting) beryllium carbonate, dehydrating beryllium hydroxide, or igniting metallic beryllium:

Igniting beryllium in air gives a mixture of BeO and the nitride Be₃N₂. Unlike the oxides formed by the other group 2 elements (alkaline earth metals), beryllium oxide is amphoteric rather than basic.

Beryllium oxide formed at high temperatures (>800 °C) is inert, but dissolves easily in hot aqueous ammonium bifluoride (NH₄HF₂) or a solution of hot concentrated sulfuric acid (H₂SO₄) and ammonium sulfate ((NH₄)₂SO₄).

BeO crystallizes in the hexagonal wurtzite structure, featuring tetrahedral Be²⁺ and O²⁻ centres, like lonsdaleite and w-BN (both of which it is isoelectronic with). In contrast, the oxides of the larger group 2 metals, i.e., MgO, CaO, SrO, BaO, crystallize in the cubic rock salt motif with octahedral geometry about the dications and dianions. At high temperature the structure transforms to a tetragonal form.