Chemistry informtion about Hydrogen Selenide (CAS NO.7783-07-5) is:
IUPAC Name: Selenium ; Hydrogen selenide
Synonyms: Dihydrogenselenide ; Electronic E-2 ; Electronice-2 ; H2Se ; Hydrogen Selenide (H2Se) ; Hydrogeneselenie ; Hydrogenselenide(H2se) ; Hydrogenselenide,Anhydrous
MF: H₂Se
MW: 80.98
Stability: Stable. Highly flammable. Readily forms explosive mixtures with air. Incompatible with oxidizing agents, acids, water, halogenated hydrocarbons.
Following is the molecular structure of  Hydrogen Selenide (CAS NO.7783-07-5) is:

 Hydrogen Selenide (CAS NO.7783-07-5)  is commonly used in the synthesis of Se-containing compounds; it adds across alkenes. Illustrative is the synthesis of selenoureas from nitriles. Also, it is used to dope semiconductors with selenium.

 H₂Se can be purchased in cylinders. A number of routes to H₂Se have been reported, which are suitable for both large and small scale preparations. H₂Se is usually prepared by the action of water on Al2Se3, concomitant with formation of hydrated alumina. A related reaction involves the acid hydrolysis of FeSe.
Al₂Se₃ + 6 H₂O ⇔ 2 Al(OH)₃ + 3 H₂Se
According to the Sonoda method, H2Se is generated from the reaction of H₂O and CO on Se in the presence of Et₃N.
H₂Se can by synthesized by the direct reaction of H₂ with elemental selenium at T > 300 °C.
H₂Se can also be prepared by means of different methods based on the in situ generation in aqueous solution of nascent hydrogen used as reducing agent, a.o., boron hydride, Marsh test and Devarda's alloy.
Elemental selenium can be recovered from H2Se through a reaction with aqueous sulfur dioxide (SO₂).
2 H₂Se + SO₂ ⇔ 2 H₂O + Se + S
Elemental selenium can also be directly obtained by reduction of selenite by strong reducing agent such as, e.g., ascorbic acid, hydrazine chlorhydrate, or hydroxylamine chlorhydrate.

Selenium and its compounds are on the Community Right-To-Know List. EPA Extremely Hazardous Substances List. Reported in EPA TSCA Inventory.

A deadly poison by inhalation. Very poisonous irritant to skin, eyes, and mucous membranes. Causes central nervous system effects in humans. An allergen. Can cause damage to the lungs and liver as well as conjunctivitis. It has been found that repeated exposures to concentrations of 0.3 ppm prove fatal to experimental animals by causing a pneumonitis, as well as injury to the liver and spleen. Causes garlic odor of breath, dizziness, nausea. Concentrations of 0.3 ppm are readily detected by odor, but there is no noticeable irritant effect at that level. Concentrations of 1.5 ppm or higher are strongly irritating to the eyes and nasal passages.
As in the case of hydrogen sulfide, the odor of hydrogen selenide in concentrations below 1 ppm disappears rapidly because of olfactory fatigue. The odor and irritating effects do not offer a dependable warning to workers who may be exposed to gradually increasing amounts and therefore become used to it. Due to its extreme toxicity and irritating effects, it seldom is allowed to reach a concentration in which it is flammable in air. Very little data are available on possible chronic effects of this material, but it is logical to assume that when the concentration of this gas is low enough to avoid the irritant effects, only the systemic effects will be noticeable.
Dangerous fire hazard when exposed to heat or flame; will react vigorously with powerful oxidizing agents, such as H₂O₂, HNO₃. Dangerous; forms explosive mixtures with air; keep away from heat and open flame. See also SELENIUM COMPOUNDS and HYDRIDES.
RIDADR: 2202
HazardClass: 2.3

OSHA PEL: TWA 0.05 ppm (Se)
ACGIH TLV: TWA 0.05 ppm (Se)
DFG MAK: 0.05 ppm (0.17 mg/m³)
DOT Classification:  2.3; Label: Poison Gas, Flammable Gas

 Hydrogen Selenide (CAS NO.7783-07-5) is a colourless gas with a very unpleasant smell.
Air & Water Reactions: Highly flammable. Soluble in water.
Reactivity Profile: It is a colorless, flammable gas of unpleasant odor, a deadly poison by inhalation. It forms explosive mixtures with air. It reacts vigorously with strong oxidizing reagents, e.g., hydrogen peroxide, nitric acid [Sax, 9th ed., 1996, p.1843].
Health Hazard: It is a hazardous compound which can cause damage to the lungs and liver. Those experiencing dermatitis, chronic bronchitis, or any form of skin allergy or respiratory tract infection are at a greater risk.
Fire Hazard: It is extremely flammable; may be ignited by heat, sparks, or flames. Vapors may travel to a source of ignition and flash back. Container may explode in heat of fire. It is dangerous and forms explosive mixtures with air.It can decompose into toxic fumes. Incompatible with acid, water, halogenated hydrocarbons, oxidizers, hydrogen peroxide, and nitric acid. It should be stored out of the direct rays of the sun. Keep away from heat and flames.