Selenium dioxide is the chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 with the formula

Chemical formula

A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 SeO₂. This colorless solid is one of the most frequently encountered compounds of selenium

Selenium

Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...

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SeO₂ is a polar molecule, with the dipole moment pointed from the midpoint of the two oxygen atoms to the selenium atom. Solid SeO₂ is a one-dimensional polymer

Polymer

A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

, the chain consisting of alternating selenium and oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 atoms. Each Se atom, which is pyramidal, bears a terminal oxide group.