Least electronegative atom will be in the central position of an molecule. But why is oxygen in the central position in the case of water?

Dear student 

The least electronegative element generally becomes the central element.
Oxygen is much more electronegative than hydrogen, which suggests that hydrogen should be the central atom, but the hydrogens are clearly peripheral atoms. This stems from the limitation that hydrogen can only form one sigma bond. That being said, hydrogen has also been found in unconventional bonding arrangements

In general least electronegative atom should be as central atom but geneal principal is not always follow in everycase ..

In a molecular compound the atom which has maximum size and least no in compound that should be taken as central atom also .

  It will help u to undetstand 

 (Kindly approved )