Question

The formula charge on the nitrogen atoms from left to right the azide ion $$[N=N=N{]}^{-}$$ are:
A.+1, -1, -1
B.-1, +1, -1
C.-1, -1, +1
D.-1, +1, 0

Answer 1

Hint: Basically, a formal charge over an atom of a polyatomic molecule or ion is the difference between the valence electron of that atom in the elemental state and the number of electrons assigned to that atom in Lewis structure. So, to solve this question we need to calculate the formal charge on nitrogen atoms.

Formula used:
Formal charge = (number of valence electron in free neutral atom) $-{\displaystyle \frac{1}{2}}$ (number of bonding electron)-(number of nonbonding electron)

Complete step by step answer:
Nitrogen is the seventh element of the periodic table and it is also an important part of amino acids. Since it has five electrons in its outermost shell, most of its compounds are trivalent. Now, the formal charge helps in the selection of the lowest energy structure from a number of possible Lewis structures for a given species. It is also known as a fake charge.
Now, the formal charge over an atom of a polyatomic molecule or ion is the difference between the valence electron of that atom in the elemental state and the number of electrons assigned to that atom in Lewis structure. So, now we will calculate the formal charge on the nitrogen atom from left to right in the ion $$[N=N=N{]}^{-}$$ .
So, according to the formula,
Formal charge = (number of valence electron in free neutral atom) $-{\displaystyle \frac{1}{2}}$ (number of bonding electron)-(number of nonbonding electron)
Now,
 $N_1=5-2-4$
=-1
 $N_2=5-4-0$
=+1
 $N_3=5-2-4$
=-1
Therefore, the formal charge from left to right are -1, +1, -1

Hence, option B is correct.

Note:Generally, the lowest energy structure is the one with the smallest formal charges. Moreover, the knowledge of the lowest energy structures helps in predicting the major product of a reaction and also describes the phenomenon.