Most of the chemistry of tellurium is characteristic of a nonmetal. It shows some cationic behaviour. The dioxide dissolves in acid to yield the trihydroxotellurium(IV) Te(OH) 3 ion; the red Te 4 and yellow-orange Te 6 ions form when tellurium is oxidized in fluorosulfuric acid (HSO 3 F), or liquid sulfur dioxide (SO 2), respectively. It can form alloys with aluminium, silver, and tin. Tellurium shows fewer tendencies to anionic behaviour than ordinary nonmetals. Its solution chemistry is characterised by the formation of oxyanions. Tellurium generally forms compounds in which it has an oxidation state of −2, +4 or +6. The +4 state is the most stable. Tellurides of composition X x Te y are easily formed with most other elements and represent the most common tellurium minerals. Nonstoichiometry is pervasive, especially with transition metals. Many tellurides can be regarded as metallic alloys. The increase in metallic character evident in tellurium, as compared to the lighter chalcogens, is further reflected in the reported formation of various other oxyacid salts, such as a basic selenate 2TeO 2 ·SeO 3 and an analogous perchlorate and periodate 2TeO 2 ·HXO 4. Tellurium forms a polymeric, amphoteric, glass-forming oxide TeO 2. It is a "conditional" glass-forming oxide – it forms a glass with a very small amount of additive. Tellurium has an extensive organometallic chemistry (see Organotellurium chemistry).