Ytterbium compounds are chemical compounds that contain the element ytterbium (Yb). The chemical behavior of ytterbium is similar to that of the rest of the lanthanides. Most ytterbium compounds are found in the +3 oxidation state, and its salts in this oxidation state are nearly colorless. Like europium, samarium, and thulium, the trihalides of ytterbium can be reduced to the dihalides by hydrogen, zinc dust, or by the addition of metallic ytterbium. The +2 oxidation state occurs only in solid compounds and reacts in some ways similarly to the alkaline earth metal compounds; for example, ytterbium(II) oxide (YbO) shows the same structure as calcium oxide (CaO).