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In my book it is given
Reducing property increases down the group in gaseous or molten state . The increasing order is Li , Na , K , Rb ,Cs
In according to me reducing property is based on ionisation property . As Cs has highest ionisation property so it can easily loose elctron (oxidation potential)
But in aqueous solution incresing order is given as Na , Cs ,Rb , k ,Li
For this what could be the reason .