The Lewis structure of CHO2– contains two single bonds and one double bond, with carbon in the center, and hydrogen and two oxygens on either side. The top oxygen atom has three lone pairs, the right oxygen atom has two lone pairs, and carbon atom and hydrogen atom do not have any lone pair.
Plus, there is a negative (-1) charge on the top oxygen atom.
Steps
By using the following steps, you can easily draw the Lewis structure of CHO2–.
#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Complete octet on central atom
#5 Calculate formal charge and check stability
Let’s one by one discuss each step in detail.
#1 Draw skeleton
In this step, first calculate the total number of valence electrons. And then, decide the central atom.
- Let’s calculate the total number of valence electrons
We know that… carbon is a group 14 element, hydrogen is a group 1 element, and oxygen is a group 16 element. Hence, carbon has four valence electrons, hydrogen has one valence electron, and oxygen has six valence electrons.
Now CHO2– has one carbon atom, one hydrogen atom, and two oxygen atoms.
So the total number of valence electrons = valence electrons of carbon atom + valence electrons of hydrogen atom + (valence electrons of oxygen atom × 2)
And CHO2– has a negative (-1) charge, so we have to add one more electron.
Therefore, the total number of valence electrons = 4 + 1 + 12 + 1 = 18
- Now decide the central atom
We can not assume hydrogen as the central atom, because the central atom is bonded with at least two other atoms. And hydrogen has only one electron in its last shell, so it can not make more than one bond.
Therefore, choose the central atom from carbon and oxygen.
The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for carbon and oxygen as follows:
Electronegativity value of carbon = 2.55
Electronegativity value of oxygen = 3.44
Obviously, carbon is less electronegative than oxygen. Hence, assume that carbon is the central atom.
So now, put carbon in the center and hydrogen and oxygens on either side. And draw the rough skeleton structure for the Lewis structure of CHO2– something like this:
Also read: How to draw Lewis structure of BrO2– (5 steps)
#2 Show chemical bond
Place two electrons between the atoms to show a chemical bond. Since carbon is surrounded by hydrogen and two oxygens, use six electrons to show three chemical bonds as follows:
#3 Mark lone pairs
As calculated earlier, we have a total of 18 valence electrons. And in the above structure, we have already used six valence electrons. Hence, twelve valence electrons are remaining.
Two valence electrons represent one lone pair. So twelve valence electrons = six lone pairs.
Note that both (carbon and oxygen) are the period 2 elements, so they can not keep more than 8 electrons in their last shell. And hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell.
Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.
The outside atoms are hydrogen and oxygens. But hydrogen can not keep more than 2 electrons in its last shell. Hence, don’t mark the lone pairs on hydrogen.
So eah oxygen will get three lone pairs. And the central atom (carbon) will not get any lone pair, because all six lone pairs are used.
Now draw the Lewis structure of CHO2– something like this:
In the above structure, you can see that the octet is completed on outside atoms. But, the central atom (carbon) doesn’t form an octet.
So in the next step, we have to complete the octet on the central atom.
Also read: How to draw Lewis structure of IF3 (4 steps)
#4 Complete octet on central atom
Remember that carbon is a period 2 element, so it can not keep more than 8 electrons in its last shell.
Now carbon already has six valence electrons. Hence, carbon needs two more valence electrons to complete its octet.
So convert one lone pair from one oxygen atom to make a new bond with the carbon atom. And then, the Lewis structure of CHO2– looks something like this:
In the above structure, you can see that the octet is completed on the central atom (carbon), and also on the outside atoms. Therefore, the octet rule is satisfied.
After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.
Also read: How to draw Lewis structure of CNO– (5 steps)
#5 Calculate formal charge and check stability
The following formula is used to calculate the formal charges on atoms:
Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons
Collect the data from the above structure and then, write it down below as follows:
- For carbon atom
Valence electrons = 4
Nonbonding electrons = 0
Bonding electrons = 8
Formal charge = 4 – 0 – ½ (8) = 0
- For hydrogen atom
Valence electrons = 1
Nonbonding electrons = 0
Bonding electrons = 2
Formal charge = 1 – 0 – ½ (2) = 0
- For top oxygen atom
Valence electrons = 6
Nonbonding electrons = 6
Bonding electrons = 2
Formal charge = 6 – 6 – ½ (2) = -1
- For right oxygen atom
Valence electrons = 6
Nonbonding electrons = 4
Bonding electrons = 4
Formal charge = 6 – 4 – ½ (4) = 0
Mention the formal charges of atoms on the structure. So the Lewis structure of CHO2– looks something like this:
In the above structure, you can see that the formal charges of atoms are closer to zero. Therefore, this is the most stable Lewis structure of CHO2–.
And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.
Now CHO2– is an ion having a negative (-1) charge, so draw brackets around the above Lewis structure and mention that charge on the top right corner. And then, the Lewis structure of CHO2– looks something like this:
Related
- Lewis structure of BrO2–
- Lewis structure of IF3
- Lewis structure of CNO–
- Lewis structure of N2O4
- Lewis structure of PF6–
External links
- CHO2- Lewis Structure in 6 Steps (With Images) – Pediabay
- How many valence electrons does CHO2- have? Use the periodic table to calculate the total – Assignment Studio
- Question about CHO2(-1) – Lewis Dot Structure – Reddit
- can someone pls drawthe lewis structure of CHO2- – Chegg
- Draw the Lewis structure for CHO2- on a piece of paper – Course Hero
- Draw the Lewis structure for CHO2- on a piece of paper – Brainly
- Draw the Lewis structure of CHO2- – Quizlet
- How to draw lewis structure for CHO2- and how do you determine the # of Atoms and Sets of Lone Pairs Surrounding Central Atom. What is it’s Structure Geometry name? – Bartleby
- Draw the Lewis structure for (CHO2)- on a piece of paper – Numerade
- CHO2- (Formate Anion) Oxidation Number – ChemicalAid
- How can I draw two equivalent resonance structures for the formate ion, HCO2-? – Socratic
Deep
Rootmemory.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.