plzz give explanation

First is you need to know the number of valence electrons. You can do this by (1) drawing the electron configuration per element or (2) consulting your periodic table.

If you chose to draw the electron configuration per element, you will have something like this:

N(atomic number = 7) :1s22s22p3(5 outermost electrons)

O(atomic number = 8) :1s22s22p4(6 outermost electrons)

If you chose to consult your periodic table, just notice thatNbelong to Group 5A whileObelongs to Group 6A. The group number denotes the number of outermost electrons.Now that you know the number of valence electrons per element, you need to compute the total valence electrons for theNO-13ion.

5 + (3 x 6) = 23 electrons

But since the whole molecule has a -1 charge, you need to add this too. So thetotal number of valence electrons is 24.

The next thing to do is draw. Normally, the first element in the chemical formula is thecentral atom. In this case, theNatom is being surrounded by threeOatoms.