NO and NO2 and NO3

NO has a single covalent bond and the extra single electron from O will delocalize between N and O.

NO2 has 1 single covalent bond and 1 double covalent bond O=N-O. The extra electron of the O will delocalize between two covalents bonds.

According to my memory, it should be no NO3.

Delocalization of the single electron (original in N, not extra) is unstable. No. of outermost shell e :
NO: N=6.5, O=8.5
NO2: N=6.5, each O=8.25
If locate at N, both become more stable (N = 7, O = 8).

In NO and NO2 molecules, each N atom has only 7 electrons in the outermost shell, but not 8.

In NO, a double bond links the two atoms together (N=O). There are 3 lone pairs of electrons on the O atom, but 2 lone pairs and 1 single electron on the N atom.

In NO2, N atom forms a double bond with one of the two O atoms (N=O) and this O atom has 2 lone pairs of electrons. N gives 2 electrons to form a dative bond with another O atoms (N→O), and this O atom has 3 lone pairs of electrons. There is also a single electron on the N atom. The structure is O=N→O and resonance occurs.
[O=N→O ↔ O←N=O)

There is no compound NO3. If it is a nitrate ion (NO3^-), N atom forms a double bond with the first O atom (N=O), a dative bond with the second O atom (N→O), and a single bond with an O^- ion (N-O^-). There is no lone pair or single electron on the N atom.