[lost]

my teacher did not no the ansewer to this qustion please help if you can?

         why are there  extra valence electrons when double bounded with a negitive atom, such as nitrate?  when bonded oxygen gets an extra electron making it have seven rather then six.  

if you can help that would be great.

[Mitch]

First, each element in nitrate has 8 electrons. There is no weird chemistry involved. Except the formal charge on one of the oxygens is 7. The reason it had the higher formal charge is because: Given an option on which element should have the higher formal charge the more electronegative element will always want to have it.