The valence electron arrangement of tungsten does not follow hund's rules. Tungsten is one of the transition metal elements in the sixth period (second long period) of the periodic table of elements VIB group. Transition metal elements are obviously different from other elements because of their unfilled valence layer d orbitals based on the eighteen-electron rule.

Tungsten diiodide (chemical formula: WI₂) is a kind of inorganic compound formed by the reaction of tungsten and iodine, which has the following chemical properties.

Tungsten diiodide (WI₂) is an inorganic compound composed of the transition metal element tungsten and the halogen element iodine. It has many chemical properties, which will be described one by one below.

A small amount of tungsten diiodide has low theoretical toxicity and will not harm health.

A tungsten iodide lamp is a kind of tungsten lamp filled with the halogen element iodine and belongs to a new generation of incandescent lamps In an iodine-tungsten lamp, the evaporation of iodine-tungsten circulating tungsten is effectively suppressed, and the problem of blackening glass shell is solved.Iodine tungsten lamp as a thermal radiation source has some potential safety hazards, so there are corresponding requirements and precautions for its installation and use.

There are tungsten vapor, iodine vapor, tungsten iodide gas and inert gas in the iodine tungsten lamp.

The tungsten filament of a tungsten iodine lamp is a conductor and can radiate visible light. A tungsten iodine lamp is a new type of electric light source, the main components are the internal tungsten filament and the external glass shell. Under the action of electric current, the spiral tungsten filament continuously gathers heat, making the temperature of the filament reach over 2000℃. Microscopically, the tungsten atom's electrons outside the nucleus are excited by heat to a high-energy state, to maintain stability and fall back to a low-energy state, the energy difference in the form of photons released, macroscopically visible luminescence phenomenon.

An iodine tungsten lamp is a kind of high-efficiency lighting fixture, which is generally composed of tungsten wire and quartz glass shell. Because of its small size and high internal temperature, the glass shell will undergo a cycle of "melting-cooling-solid reheating" after use. If there is an impurity attached to the bulb shell and the surface treatment is not carried out in time, the atomic arrangement of quartz glass will change at high temperatures, causing the surface to crystallize and lose its transparency. This phenomenon is called devitrification.

Quartz glass can be used as bulb shell of iodine tungsten lamp.Iodine tungsten lamp is one of the first choice products in green lighting engineering in China. It has the characteristics of high light efficiency, small volume and energy saving, and is suitable for the design and shape of various lamps and lanterns. It is widely used in lighting field.

Ordinary glass cannot be used as a bulb shell for an iodine tungsten lamp. The iodine tungsten lamp is a kind of illumination lamp that uses the principle of halogen-tungsten circulation to fill iodine into the bulb to control the sublimation of the tungsten wire. It has the characteristics of high brightness and long life. It is often used as the light source of cinematography stage factory building square.