How do you draw the Lewis Structure for #HNO_3#?
The left most oxygen is neutral (with 2 lone pairs, and with the double bond it has the 6 valence electrons required for neutrality). The nitrogen has a share of 4 electrons, and thus is formally positive (i.e. with 2 inner core electrons, there are 6 electrons only to balance the +7 nuclear charges. To balance this positive charge, the next oxygen has 7 valence electrons (9 in total), and thus a formal negative charge. The hydroxyl group is formally neutral.