Lewis structure of SeO2

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The Lewis structure of SeO₂ contains two double bonds, with selenium in the center, and two oxygens on either side. There are two lone pairs on each oxygen atom, and one lone pair on the selenium atom.

Steps

By using the following steps, you can easily draw the Lewis structure of SeO₂:

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Complete octet on central atom
#5 Calculate formal charge and check stability
#6 Convert lone pair and calculate formal charge again (if formal charges are not closer to zero)

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… both selenium and oxygen are the group 16 elements. Hence, both selenium and oxygen have six valence electrons.

Now SeO₂ has one selenium atom and two oxygen atoms.

So the total number of valence electrons = valence electrons of selenium atom + (valence electrons of oxygen atom × 2)

Therefore, the total number of valence electrons = 6 + 12 = 18

• Now decide the central atom

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for selenium and oxygen as follows:

Electronegativity value of selenium = 2.55
Electronegativity value of oxygen = 3.44

Obviously, selenium is less electronegative than oxygen. Hence, assume that selenium is the central atom.

So now, put selenium in the center and oxygens on either side. And draw the rough skeleton structure for the Lewis structure of SeO₂ something like this:

Also read: How to draw Lewis structure of ICl₄^– (4 steps)

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since selenium is surrounded by two oxygens, use four electrons to show two 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 four valence electrons. Hence, fourteen valence electrons are remaining.

Two valence electrons represent one lone pair. So fourteen valence electrons = seven lone pairs.

Note that selenium is period 4 element, so it can keep more than 8 electrons in its last shell. And oxygen is a period 2 element, so it can not keep more than 8 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 oxygens, so each oxygen will get three lone pairs. And the central atom (selenium) will get one lone pair.

So the Lewis structure of SeO₂ looks something like this:

In the above structure, you can see that the octet is completed on outside atoms. But, the central atom (selenium) 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 SiCl₄ (4 steps)

#4 Complete octet on central atom

Remember that selenium is a period 4 element, so it can keep more than 8 electrons in its last shell.

Now selenium already has six valence electrons. Hence, selenium 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 selenium atom. And then, the Lewis structure of SeO₂ looks something like this:

In the above structure, you can see that the octet is completed on the central atom (selenium), 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.

#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 selenium atom

Valence electrons = 6
Nonbonding electrons = 2
Bonding electrons = 6

Formal charge = 6 – 2 – ½ (6) = +1

• For left oxygen atom

Valence electrons = 6
Nonbonding electrons = 4
Bonding electrons = 4

Formal charge = 6 – 4 – ½ (4) = 0

• For right oxygen atom

Valence electrons = 6
Nonbonding electrons = 6
Bonding electrons = 2

Formal charge = 6 – 6 – ½ (2) = -1

Mention the formal charges of atoms on the structure. So the Lewis structure of SeO₂ looks something like this:

In the above structure, you can see that the formal charges of atoms are not closer to zero. Therefore, convert lone pair and calculate formal charge again.

Also read: How to draw Lewis structure of SiF₄ (4 steps)

#6 Convert lone pair and calculate formal charge again

As mentioned earlier, selenium is a period 4 element, so it can keep more than 8 electrons in its last shell.

So again convert one lone pair from the right oxygen atom to make a new bond with the selenium atom. And then, the Lewis structure of SeO₂ looks something like this:

Now one last thing we need to do is, calculate the formal charge again and check the stability of the above structure.

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 selenium atom

Valence electrons = 6
Nonbonding electrons = 2
Bonding electrons = 8

Formal charge = 6 – 2 – ½ (8) = 0

• For each 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 SeO₂ looks something like this:

In the above structure, you can see that the formal charges of both (selenium and oxygen) are zero. Therefore, this is the stable Lewis structure of SeO₂.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

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Related

• Lewis structure of ICl₄^–
• Lewis structure of SiCl₄
• Lewis structure of SiF₄
• Lewis structure of OCN^–
• Lewis structure of CH₃F

External video

• SeO2 Lewis Structure – How to Draw the Lewis Structure for SeO2 – YouTube • Wayne Breslyn

External links

• How do you draw the Lewis structure for SeO2. What is the electron geometry around the central atom? – Socratic
• SeO2 Lewis Structure, Molecular Geometry, Shape and Bond Angle – Geometry of Molecules
• SeO2 Lewis structure, molecular geometry, bond angle, hybridization – Topblogtenz
• SeO2 Lewis Structure in 6 Steps (With Images) – Pediabay
• SeO2 Lewis Structure, Geometry, Hybridization, and Polarity – Techiescientist
• Drawing the Lewis Structure for SeO2 – The Geoexchange
• Draw the Lewis structure for the selenium dioxide – Chegg
• Draw the Lewis structure of SeO2 – Homework.Study.com
• Why is the correct Lewis structure for SeO2 the second one (the one with the double bonds) but not the first? – Reddit
• Draw the Lewis structure for the selenium dioxide molecule – Brainly
• SeO2 lewis structure – Laurence Lavelle