Does the nitrate ion have one long ##N¬O## bond and two short ##N¬O## bonds?

If anything, you might predict that NO₃⁻ has one short N-O bond and two long ones. But all N-O bonds in NO₃⁻ are the same length.

You can draw three equivalent Lewis structures for NO₃⁻. Each has an N=O double bond and two N-O single bonds.

The actual structure is none of these. It is a resonance hybrid of them all.

All three bonds have exactly the same length.