Q36E_b

Question

Question: Assign formal charges to the atoms in each of the following molecules:

Step-by-Step Solution

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Answer

Answer

The formal charge on all H in is 0

The formal charge on C in is 0

The formal charge on N at left is -1

The formal charge on N in the middle is +1

The formal charge on N at the rightmost is 0.

1Step 1: Formal charge

Formal charge means electric charge present on an atom in a molecule. It indicates the magnitude and whether the charge is positive or negative.

2Step 2: Calculation of formal charge

The formal charge on an atom is equal to the number of valence electrons in a neutral and isolated atom minus the number of electrons present in its bonded atom form in a molecule. The number of electrons in a bonded atom is calculated as half the number of bonding electrons plus the nonbonding, that is, lone-pair electrons.

$F o r m a l C h a r g e = (N u m b e r o f v a l e n c e e l e c t r o n s i n f r e e a t o m) - (N u m b e r o f v a l e n c e e l c t r o n s i n b o n d e d a t o m) = (N u m b e r o f v a l e n c e e l e c t r o n i n f r e e a t o m) - (\frac{N u m b e r o f b o n d i n g e l e c t r o n}{2} + N u m b e r o f n o n b o n d i n g e l e c t r o n)$

3Step 3: Calculation of formal charge on all H in C H 3

Using the above formula:

$F o r m a l c h a r g e = (N u m b e r o f v a l e n c e e l e c t r o n i n f r e e a t o m) - (\frac{N u m b e r o f b o n d i n g e l e c t r o n}{2} + N u m b e r o f n o n b o n d i n g e l e c t r o n) = 1 - (\frac{2}{2} + 0) = 1 - 1 = 0$

4Step 4: Calculation of formal charge on N bonded with C H 3

Using the above formula:

$F o r m a l c h a r g e = (N u m b e r o f v a l e n c e e l e c t r o n i n f r e e a t o m) - (\frac{N u m b e r o f b o n d i n g e l e c t r o n}{2} + N u m b e r o f n o n b o n d i n g e l e c t r o n) = 5 - (\frac{4}{2} + 4) = 5 - 6 = - 1$

5Step 4: Calculation of formal charge on N in the middle

Using the above formula:

$F o r m a l c h a r g e = (N u m b e r o f v a l e n c e e l e c t r o n i n f r e e a t o m) - (\frac{N u m b e r o f b o n d i n g e l e c t r o n}{2} + N u m b e r o f n o n b o n d i n g e l e c t r o n) = 5 - (\frac{8}{2} + 0) = 5 - 4 = 1$

6Step 5: Calculation of formal charge on all C in C H 3

Using the above formula:

$F o r m a l c h a r g e = (N u m b e r o f v a l e n c e e l e c t r o n i n f r e e a t o m) - (\frac{N u m b e r o f b o n d i n g e l e c t r o n}{2} + N u m b e r o f n o n b o n d i n g e l e c t r o n) = 4 - (\frac{8}{2} + 0) = 4 - 4 = 0$

7Step 6: Calculation of formal charge on rightmost N

Using the above formula:

$F o r m a l c h a r g e = (N u m b e r o f v a l e n c e e l e c t r o n i n f r e e a t o m) - (\frac{N u m b e r o f b o n d i n g e l e c t r o n}{2} + N u m b e r o f n o n b o n d i n g e l e c t r o n) = 5 - (\frac{6}{2} + 2) = 5 - 5 = 0$

Q36E_a

Q36E_c

Other exercises in this chapter

Q30E

Which of the following molecules has a dipole moment? Indicate the expected direction of each.

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Q36E_a

Assign formal charges to the atoms in each of the following molecules:

View solution

Q36E_c

Question: Assign formal charges to the atoms in each of the following molecules:

View solution

Q36E

Assign formal charges to the atoms in each of the following molecules:a.b.c.

View solution