How to draw the lewis structure of carbon monoxide

How to draw the Lewis structure of carbon monoxide, CO

By José @ Periodic table with names

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Steps to draw 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 oxygen 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 CO

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

• Total valence e. from O: 66 e. x 1O = 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 CO

• Carbon should have 8 valence electrons

• Oxygen 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 monoxide, CO

O C

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

For CO

• Oxygen has 6 valence electrons:

CO

For CO

• Carbon has 4 valence electrons:

CO

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.

CO

For CO

Single bond

CO

CO

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

Oxygen atom has 7 electrons, it needs 8

CO

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

Carbon atom has 5 electrons, it needs 8

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

CO

CO

Pair another couple of electrons for each atom:

Now count the number of electrons around each atom:

Oxygen has 8 electrons

CO

Now count the number of electrons around each atom:

But carbon only 6!

CO

In order for carbon to have 8 electrons, oxygen must donate 2 electrons to participate in a bond:

CO

In order for carbon to have 8 electrons, oxygen must donate 2 electrons to participate in a single bond:

CO

Now carbon is also surrounded by 8 electrons:

CO

Now we just need to change the dots for lines to represent a triple bond:

CO

Practice writing the Lewis structure of any other molecule!

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