## Chemistry and Chemical Reactivity (9th Edition)

$B.O.=N.\ Shared\ pairs\div N.\ links$ $NO_2^+$: $4/2=2$ $NO_2^-$: $3/2=1.5$ Since bond length decreases with bond order, the 110 pm is from $NO_2^+$ and the 124 pm is from $NO_2^-$.