Question

loudon | parise seventh edition
consider the incomplete structure. add formal charges as necessary to the structure. all unshared valence electrons are shown.
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add formal charges.
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c h h o
what is the net charge on the species?
-1
+1
0
+2
-2

Explanation:

Step1: Calculate O formal charge

Formal charge formula: $FC = V - N - \frac{B}{2}$, where $V$=valence electrons, $N$=nonbonding electrons, $B$=bonding electrons.
For O: $V=6$, $N=6$, $B=2$.
$FC = 6 - 6 - \frac{2}{2} = -1$

Step2: Calculate C formal charges

For each $CH_3$ C and central C: $V=4$, $N=0$, $B=8$.
$FC = 4 - 0 - \frac{8}{2} = 0$

Step3: Calculate H formal charges

For all H: $V=1$, $N=0$, $B=2$.
$FC = 1 - 0 - \frac{2}{2} = 0$

Step4: Sum all formal charges

Net charge = $(-1) + 0+0+0+0+0+0+0 = -1$

Answer:

-1 (corresponding to the option $\boldsymbol{-1}$)
The formal charge on the oxygen atom is $-1$, and all other atoms have a formal charge of $0$.