Lewis structure of SeO32-

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The Lewis structure of SeO₃^2- contains one double bond and two single bonds, with selenium in the center, and three oxygens on either side. The top oxygen atom has two lone pairs, the left oxygen atom and right oxygen atom has three lone pairs, and the selenium atom has one lone pair.

Plus, there is a negative (-1) charge on the left oxygen atom and right oxygen atom.

Steps

By using the following steps, you can easily draw the Lewis structure of SeO₃^2-.

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

Now SeO₃^2- has one selenium atom and three oxygen atoms.

So the total number of valence electrons = valence electrons of selenium atom + (valence electrons of oxygen atom × 3)

And SeO₃^2- has a negative (-2) charge, so we have to add two more electrons.

Therefore, the total number of valence electrons = 6 + 18 + 2 = 26

• 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 SeO₃^2- something like this:

Also read: How to draw Lewis structure of P₄ (4 steps)

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since selenium is surrounded by three oxygens, use six electrons to show three chemical bonds as follows:

#3 Mark lone pairs

As calculated earlier, we have a total of 26 valence electrons. And in the above structure, we have already used six valence electrons. Hence, twenty valence electrons are remaining.

Two valence electrons represent one lone pair. So twenty valence electrons = ten lone pairs.

Note that selenium is a 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 SeO₃^2- 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.

Now calculate the formal charge and check the stability of the above structure.

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

#4 Complete octet on central atom

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 each 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 SeO₃^2- 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 NH₂OH (4 steps)

#5 Calculate formal charge and check stability

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

So convert one lone pair from one oxygen atom to make a new bond with the selenium atom. And then, the Lewis structure of SeO₃^2- 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 top oxygen atom

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

Formal charge = 6 – 4 – ½ (4) = 0

• For left oxygen and 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 SeO₃^2- 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 SeO₃^2-.

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

Now SeO₃^2- is an ion having a negative (-2) charge, so draw brackets around the above Lewis structure and mention that charge on the top right corner. And then, the Lewis structure of SeO₃^2- looks something like this:

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Related

• Lewis structure of P₄
• Lewis structure of ClF
• Lewis structure of NH₂OH
• Lewis structure of S₂O
• Lewis structure of C₂HCl

External links

• We can draw three inequivalent Lewis structures for the selenite ion, Seo32- – Chegg
• Draw the Lewis structure for the SeO3-2 ion, then using VSEPR theory, what is its geometry and electronic structure? – Brainly
• SeO32- (Selenite Ion) Oxidation Number – ChemicalAid
• Give the Lewis structure for the selenite ion, SeO32- – OneClass
• How is the hybridization of SO3 2-determined? – Quora