Zirconium has four valance electrons, with two in the 4d level and two in the 5s level. This allows it to combine with other elements and ions in different configurations. It has valence charges of +2, +3 and +4.
The most common valance charge of zirconium is +4. Like aluminum, zirconium forms a protective oxide in air. If zirconium is ignited, it burns in air. OSHA limits the exposure of workers to zirconium to 5 milligrams per cubic meter of air due to its potential for absorption into the body through inhalation, the skin or eyes. Zirconium is common in building nuclear reactors, as it does not readily absorb neutrons. It is also an important for catalytic converters found on automobiles.