We can determine the valency of nitrogen in N_{2}O_{5}by calculating its oxidation state in the compound. The valency will be numerically equal to the oxidation state. We know that oxygen shows an oxidation state of -2 (except in oxides and superoxides). Let us assume that the oxidation state of nitrogen is 'a'. Thus we have

2a + 5 x (-2) = 0

This gives a = 5

Thus, the valency of nitrogen in N_{2}O_{5}will be 5

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Covalency is the maximum number of orbital available for sharing of electrons. In N2O5 the maximum number of Orbitals of Nitrogen atoms available are 4 and they are 2S, 2Px,2Py,2Pz. Hence covalency of Nitrogen in N2O5 is 4. To explain further since in N2O5 the oxidation state of Nitrogen is +5, therefore it means it has utilised all the two electrons availalbe in 2S and all the three electrons availble in 2Px,2Py,2Pz therefore since total of 04 orbital are involved in the formation of N2O5 so covalency is 4

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