How to write the Lewis structure of carbon disulfide, CS2

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Steps to write the Lewis structure

1. Find the number of valence electrons for each of the atoms in the molecule.

The number of valence electrons is usually the same as the group number where the element is located.

The number of valence electrons for carbon is 4 (group 4)

The number of valence electrons for sulfur is 6 (group 6)

2. Count the total number of valence electrons in the molecule:

Sum the valence electrons from each atom in the molecule

For CS2

• Total valence e. from C: 44 e. x 1 C = 4

• Total valence e. from S: 66 e. x 1s = 6

Total valence e. in the molecule: 4 + 6 = 10

3. Use the octet rule to figure how many octet electrons the atoms should have:

Most atoms need 8 electrons to complete their valence shield

Hydrogen is an exception and needs only 2

For CS2

• Carbon should have 8 valence electrons

• Sulfur should have 8 valence electrons

4. Draw an initial sketch of the molecule by placing the symbol of each atom in a diagram

For carbon disulfide, CS2

S C S

5. Place the valence electrons of each atom around them, starting from the outer atoms

For CS2

• Sulfur has 6 valence electrons:

CS S

For CS2

• Carbon has 4 valence electrons:

CS S

6. Each bond in a molecule is made up from two electrons.

Each atom in the molecule need to be bonded together to its nearest atom.

CS S

For CS2

CS S

For CS2

Bond

CS S

Bond

CS S

Count the number of electrons each atom has after forming a single bond:

Each sulfur atom has 7 electrons, it needs 8

CS S

Count the number of electrons each atom has after forming a single bond:

Carbon atom has 6 electrons, it needs 8

To complete the octet we would need to pair another couple of electrons for each sulfur atom

CS S

CS S

To complete the octet we would need to pair another couple of electrons for each sulfur atom

To complete the octet we would need to pair another couple of electrons for each sulfur atom

CS S

Now count the number of electrons around each atom: each atom should have 8 electrons

CS S

Each sulfur has 8 electrons around, its valence is complete.

CS S

Carbon has 8 electrons around, its valence is complete.

CS S

Practice writing the Lewis structure of any other molecule!

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