Oxygen ( /ˈɒksɨdʒɨn/ ok-si-jin) is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς (oxys) ("acid", literally "sharp", referring to the sour taste of acids) and -γενής (-genēs) ("producer", literally "begetter"), because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a very pale blue, odorless, tasteless diatomic gas with the formula O₂.