Hydrogen ion by itself is a bare proton with very small size $(~{10}^{-15}mradius)$ and intense electric field, binds itself  with the water molecule at one of the two available lone pairs on it giving $H_3{O}^{+}.$ This species has been detected in many compounds (eg. $H_3{O}^{+}C{l}^{-}$ )  in the solid state. In aqueous solution the hydronium ion is further hydrate to give species like $H_5{O}_2^{+},H_7{O}_3^{+}and{H}_9{O}_4^{+}.$ Similarly the hydroxyl ion is hydrated to give several ionic species like $H_3{O}_2^{-},H_5{O}_3^{-}and{H}_7{O}_4^{-}etc.$ Then number of hydrogen bonds in $H_9{O}_4^{+}$ is