Draw the best Lewis structure for CH₃^-. What is the formal charge on the C? A) 0 B) 1 C) -1 D) 2 E) -2

Question

Quizplus · Accepted Answer

To draw the Lewis structure, we first need to count the number of valence electrons in the molecule.

C: 4
H: 1 x 13 = 13
S: 1 x 2 + 1 x 1 = 3
P: 1
O: 2 x 1 = 2
Total: 23

We start by placing the atoms in a way that satisfies the octet rule for all atoms.

H
             |
H – C – S = P = S – P – S
             |
             H

Each H atom has 2 electrons, each S,P,O has 8 electrons, and the C has 4 electrons, for a total of 22 electrons. This leaves 1 electron, which we can place on the C to complete its octet:

H
             |
H – C = S = P = S – P – S
      ||     |
      O      H

The formal charge on an atom is the difference between the number of valence electrons of the free atom and the number of electrons assigned to that atom in the Lewis structure.

For the C atom, the number of valence electrons in the free atom is 4, and the Lewis structure has 4 electrons assigned to it (2 from the double bond to S and 2 from the single bond to H), so the formal charge on the C is:

FC = 4 – (2 + 2) = 0

Therefore, the answer is A) 0.

Draw the Best Lewis Structure for CH3-

Draw the Best Lewis Structure for CH₃^-