for the dimethylthiocarbamate ion [OSCN(CH3)2]-.

Add bonds and electron lone pairs in order to give the important resonance structures of this
ion, including any formal charges where necessary. Select the resonance structure likely to
provide the best description of this ion. (please explain it)

Thank you!

This forum doesn't allow us to draw structures (Lewis or otherwise). You might try to google it.

To determine the important resonance structures of the dimethylthiocarbamate ion [OSCN(CH3)2]-, we need to consider the possible arrangements of bonds and electron lone pairs.

Starting with the skeleton structure of the ion, we have:

[O - S - C - N(CH3)2]-

In this structure, the oxygen atom (O) carries a formal charge of -1. To determine the resonance structures, we can rearrange the electrons in the molecule, while keeping the atoms in the same positions.

There are two primary resonance forms to consider:

Resonance Structure 1:
[O = S - C - N(CH3)2]-

In this structure, we can see that the double bond has been formed between the oxygen and sulfur atoms. This results in the sulfur atom carrying a formal charge of -1, while the oxygen atom carries no charge.

Resonance Structure 2:
[O = C - S - N(CH3)2]-

In this structure, the double bond has been formed between the oxygen and carbon atoms. This results in both the sulfur and carbon atoms carrying a formal charge of -1.

Now, let's evaluate which resonance structure provides the best description of the ion. To do so, we consider the electronegativity of the atoms involved. Oxygen (O) is more electronegative than sulfur (S), and sulfur is more electronegative than carbon (C). Therefore, the oxygen atom is the best candidate to carry a negative charge.

Thus, the resonance structure likely providing the best description of the dimethylthiocarbamate ion is:

[O = S - C - N(CH3)2]-

In this structure, the oxygen atom carries a formal charge of -1, while the sulfur, carbon, and nitrogen atoms have no charges. This resonance structure best represents the distribution of electrons in the molecule and is considered the most significant resonance form.

To determine the important resonance structures of the dimethylthiocarbamate ion [OSCN(CH3)2]-, it is helpful to first understand the Lewis structure of the ion.

1. Start by determining the total number of valence electrons. Since the dimethylthiocarbamate ion is negatively charged, add one additional electron to the total number of valence electrons of dimethylthiocarbamate (16 + 2(3) + 2 = 24).

2. Place the atoms in the Lewis structure, starting with the central atom (sulfur, S) and then arranging the other atoms around it. Connect each atom to the central atom using a single bond.

O-S-C-N-C
| |
CH3 CH3

3. Distribute the remaining electrons around the atoms, starting with the outer atoms. Fill the octets of the atoms with their respective valence electrons, except for hydrogen, which only needs two electrons. In this case, sulfur (S) has 6 electrons around it (two in the oxygen-oxygen bond and two in the oxygen-sulfur bond), and the carbon (C) and nitrogen (N) each have 8 electrons around them (with four bonds and zero lone pairs).

4. Count the remaining electrons to determine if the octets of all atoms have been filled. In this case, there are 24 - 24 = 0 electrons remaining.

Now, to determine the resonance structures, we need to examine the movement of electrons.

5. Move a lone pair of electrons from one atom (typically a more electronegative atom) towards another atom (typically a less electronegative atom) through the pi (π) bond. It is important to maintain the octet rule for each atom and retain the overall charge. In this case, the most likely electron movement occurs from the sulfur atom towards the carbon atom.

O=C-S+N(CH3)2

6. Redraw the structure with the new electron movement, including any changes in bond lengths and formal charges. In this case, the carbon atom now has a double bond with the sulfur atom, and the sulfur atom has an additional electron lone pair.

O=C=S-N(CH3)2

7. Evaluate if there are additional possible resonance structures by moving electrons between atoms following step 5. In this case, there are no other possible resonance structures since all atoms are already surrounded by an octet.

Finally, to determine the best description of the ion:

The resonance structure likely to provide the best description of the dimethylthiocarbamate ion is the one with a double bond between the carbon and sulfur atoms (O=C=S-N(CH3)2). This is because sulfur is more electronegative than carbon, and atoms typically prefer to retain their octet with a double bond.

Note that the formal charge on each atom should be calculated and considered, but without more information given in the question, it is not possible to provide specific values.