Selenium dioxide

Selenium dioxide
	Selenium dioxide
	Ball-and-stick model of a chain in crystalline selenium dioxide
	Crystals of selenium dioxide
Names
	Other names Selenium(IV) oxide; Selenous anhydride
Identifiers
CAS Number	7446-08-4 ;
3D model (JSmol)	monomer: Interactive image; polymer: Interactive image;
ChEMBL	ChEMBL3183452;
ChemSpider	22440 ;
ECHA InfoCard	100.028.358
EC Number	231-194-7;
PubChem CID	24007;
RTECS number	VS8575000;
UNII	9N3UK29E57 ;
UN number	3283
CompTox Dashboard (EPA)	DTXSID4021264 ;
	InChI InChI=1S/O2Se/c1-3-2 Key: JPJALAQPGMAKDF-UHFFFAOYSA-N ; InChI=1/O2Se/c1-3-2 Key: JPJALAQPGMAKDF-UHFFFAOYAQ;
	SMILES monomer: O=[Se]=O; polymer: O[Se](=O)O[Se](=O)O[Se](=O)O[Se](=O)O[Se](=O)O[Se](=O)O[Se](=O)O[Se](=O)O[Se](=O)O[Se](=O)O[Se](=O)O[Se](=O)O[Se](=O)O[Se](=O)O[Se](=O)O;
Properties
Chemical formula	SeO2
Molar mass	110.969 g·mol−1
Appearance	White tetragonal needles or powder
Odor	rotten horseradish
Density	3.95 g/cm3, solid
Melting point	360 °C (680 °F; 633 K) (sealed tube)
Boiling point	315 °C (599 °F; 588 K) (sublimation point)
Solubility in water	263.4 g/100mL (22 °C (72 °F; 295 K), forms selenous acid)
Solubility in ethanol	soluble
Solubility in acetone	slightly soluble
Solubility in methanol	soluble
Vapor pressure	1 Pa (124.5 °C (256.1 °F; 397.6 K)); 1 kPa (228 °C (442 °F; 501 K)); 100 kPa (315 °C (599 °F; 588 K));
Band gap	3.29 eV
Magnetic susceptibility (χ)	−27.2×10−6 cm3/mol
Dipole moment	2.62±0.05 D
Structure
Crystal structure	Tetragonal
Space group	P42/mbc
Point group	4/mmm
Lattice constant	a = 8.37 Å, b = 8.37 Å, c = 5.08 Å α = 90°, β = 90°, γ = 90°
Lattice volume (V)	356.23 Å3
Formula units (Z)	8
Thermochemistry
Std enthalpy of; formation (ΔfH⦵298)	−225.4 kJ/mol
Enthalpy of fusion (ΔfH⦵fus)	17.6 kJ/mol
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Toxic by ingestion and inhalation
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301+H331, H373, H410
Precautionary statements	P260, P264, P270, P271, P273, P301+P310+P330, P304+P340+P311, P314, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)	4 0 1
Flash point	Non-flammable
Threshold limit value (TLV)	0.2 mg/m3 (TWA)
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	48 mg/kg (oral, rat); 4 mg/kg (dermal, rabbit);
LCLo (lowest published)	5890 mg/m3 (rabbit, 20 min); 6590 mg/m3 (goat, 10 min); 6590 mg/m3 (sheep, 10 min);
	NIOSH (US health exposure limits):
PEL (Permissible)	0.2 mg/m3
REL (Recommended)	0.2 mg/m3
IDLH (Immediate danger)	1 mg/m3 (as Se)
Related compounds
Other cations	Ozone; Sulfur dioxide; Tellurium dioxide;
Related selenium oxides	Selenium trioxide
Related compounds	Selenous acid; Selenium disulfide;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Selenium dioxide is the chemical compound with the formula SeO₂. This colorless solid is one of the most frequently encountered compounds of selenium. It is used in making specialized glasses as well as a reagent in organic chemistry.