Q.What is the covalence of nitrogen in N2O5 ?

Step 1 — Structure of $N_2O_5$.

$N_2O_5$ consists of two $-NO_2$ groups joined through a bridging oxygen atom: $O_2N\!-\!O\!-\!NO_2$. Each nitrogen is bonded to: one bridging O (single bond), and two terminal O atoms (one as N=O double bond, one as N–O single bond with formal charge, via resonance both terminal N–O bonds are equivalent).

Step 2 — Counting covalency.

Covalency = number of shared electron pairs (bonds) around the atom, counting a double bond as 2. For each N: 1 (bridging O, single) + 1 (terminal O, single) + 2 (terminal O, double N=O) = 4 total bonds.

Step 3 — Consistency check. …

Draw out the full Lewis structure of $N_2O_5$ (bridging O connecting two –NO₂ groups) and count the total number of bonds (single + double, w …

• Don't confuse "covalency" with "oxidation state" — nitrogen's oxidation state in $N_2O_5$ is +5, but its covalency (number of bonds formed) is 4, since covalency counts bonds while oxidation state is a formal b …