As potassium is larger than sodium, potassium's valence electron is at a greater distance from the attractive nucleus and is so removed more easily than sodium's valence electron. As it is removed more easily, it requires less energy, and can be said to be more reactive.
Since it dissolves in water but doesn't conduct electricity means its not forming ions like salt. since it dissolves though it means it has to have some charge on the molecule to bond with water molecules. suger would be an example.
