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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3cb051

The thiocyanate ion can be written as (I) $S - C \equiv N$ with a negative charge on S, (II) $S = C = N$ with a negative charge on N and (III) $S \equiv C - N$ . Which of the following statements are correct?

AIn I, the formal charge on N is $- 1$
BIn II, the formal charge on N is $- 1$ and on S and C is $0$
CIn III, the formal charges are $+ 1$ on S and $- 2$ on N
DIn every structure the sum of formal charges is $- 1$

Answer: B, C, D

I: S has 1 bond and 3 lone pairs (

- 1

), C is 0, N has a triple bond and one lone pair (0), so the first statement is false. II: S 0, C 0, N has 2 bonds and 2 lone pairs (

5 - 4 - 2 = - 1

) is true. III: S has 3 bonds, 1 lone pair (

+ 1

), N has 1 bond, 3 lone pairs (

- 2

), C 0: true. Each sums to the ion charge

- 1

.

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