In the hydration of an alkene carbocation is formed from :
Carbonation
Oxonium ion
hydroxide ion
hydride ion
the hydration of an alkene is formed by oxonium ions.
Oxonium ion is a charged ion that is positive charge and has three hydrogen atoms bond to oxygen. The ion is formed by the interaction of water and hydrogen ions, released from acidic solution. It is generated along with an intermediate during hydration of alkene carbocation.