What is the hybridization and geometry of SO32?

Name of Molecule Sulfite or sulphite Molecular geometry of SO 3 2 - Trigonal pyramidal Electron geometry of SO 3 2 - Tetrahedral Hybridization Sp 3 Polarity Polar molecule 4 more rows Dec 30, 2022

What is the hybridization of the SO32 orbital?

The hybridization of the central atom is sp3 and the final structure of SO32- is trigonal pyramid .

How do you find hybridization?

An easy way to figure out what hybridization an atom has is to just count the number of atoms bonded to it and the number of lone pairs . Double and triple bonds still count as being only bonded to one atom. Use this method to go over the above problems again and make sure you understand it.

What is the bond angle of sp3 hybridization?

sp 3 Hybridization The arrangement is tetrahedral with a bond angle of 109.5 o .

What is the shape and angle of sp3 hybridization?

sp 3 hybrid orbitals are oriented at bond angle of 109.5 o from each other. This 109.5 o arrangement gives tetrahedral geometry (Figure 4).

What is trigonal or sp2 hybridization?

The sp 2 hybridization is the mixing of one s and two p atomic orbitals , which involves the promotion of one electron in the s orbital to one of the 2p atomic orbitals. The combination of these atomic orbitals creates three new hybrid orbitals equal in energy-level.

How do you find the shape and hybridization?

Hint: Shape and hybridization of a molecule can be calculated by using some rules i.e. first write the Lewis structure then calculate the number of sigma bonds and lone pair then determine the steric number (steric number is composed of number of lone pairs and sigma bonds) and then finally assign the hybridization and ...

How many bonding pairs are there in so32?

There is one double bond, two single bonds and one lone pair on the central atom that is sulphur. The molecular structure of sulfite anion is trigonal pyramidal, with bond angle of ${109.5^ \circ }$ .

What is the difference between SO3 and so32?

In SO3 there are three double bonds, and no lone pairs at sulfur. Adding two extra electrons changes that by giving two more electrons to sulfur. SO3 is sulfate trioxide, while SO3 -2 is called the sulfite ion .

What is the bond order of SO3?

As a simplistic explanation, the above sources state that the lewis structure of SO3 contains a 2+ charge on the central sulfur and negative charges on two of the three bonded oxygen atoms. In that case, SO3 contains one double bond and two single bonds , which is why people tend to list the overall bond-order as 1.33.

What does a SO3 hybrid orbital contain?

So sp3 hybrid orbital contains 1/4 s character and 3/4 p-character .

What is the bond angle of 2 double bonds?

Double-bonded carbons are sp 2 -hybridized, and have trigonal planar shapes, with the bonded atoms at angles of 120° to each other. Free rotation is not possible around carbon-carbon double bonds in alkenes, making the carbon chains less flexible and "floppy" than those of alkanes with the same number of carbons.

What is the molecular geometry of s2o3 2?

The molecular formula of thiosulfate is S2O32-. Its molecular geometry is described as a tetrahedral shape .

What is a bond angle in so2?

Sulfur dioxide is an angular molecule with a bond angle of. 119.32° and two equal S-0 bond lengths of 0.143 nm (1).

SO32- lewis structure, molecular geometry, hybridization, and bond angle (2024)

The Lewis structure of sulfite [SO₃]^2- ion is made up of a sulfur (S) atom and three oxygen (O) atoms. The sulfur (S) is present at the center of the molecular ion while oxygen (O) occupies the terminals, one on each side.

There are a total of 4 electron density regions around the central S atom in the Lewis structure of [SO₃]^2-. Out of these 4 electron density regions, there are 3 bond pairs and 1 lone pair of electrons which is situated on the central sulfur atom.

Drawing the Lewis structure of sulfite SO₃^2- is not that difficult. You just need to grab a paper and pencil and follow the instructions given below and you will learn to draw the Lewis dot structure of sulfite within no time.

Steps for drawing the Lewis dot structure of SO₃^2-

1. Count the total valence electrons in SO₃^2-

The Lewis dot structure of a molecule is referred to as a simplified representation of all the valence electrons present in it. Therefore, the very first step while drawing the Lewis structure of SO₃²^–is to count the total valence electrons present in the concerned elemental atoms.

There are two different elemental atoms present in the sulfite [SO₃]^2- ion, i.e., sulfur (S) atom and oxygen (O) atoms. When you look through the Periodic Table of elements, you will find that both sulfur (S) and oxygen (O) are located in Group VI A. So both sulfur and oxygen contain a total of 6 valence electrons in each atom.

Total number of valence electrons in Sulfur = 6
Total number of valence electrons in Oxygen = 6

The [SO₃]^2- ion consists of 1 S-atom and 3 O-atoms. Thus, the valence electrons in the Lewis dot structure of [SO₃]^2- = 1(6) + 3(6) = 24 valence electrons.

However, the twist here is that the [SO₃]^2- ion carries a negative (-2) charge which means 2 extra valence electrons are added in this Lewis structure.

∴ Hence, the total valence electrons available for drawing the Lewis dot structure of [SO₃]^2- = 24+2 = 26 valence electrons.

2. Choose the central atom

Electronegativity is defined as the ability of an atom to attract a shared pair of electrons from a covalent chemical bond. So, the atom which is least electronegative or most electropositive is placed at the centre of a Lewis structure. This is because this atom is most likely to share its electrons with the more electronegative atoms surrounding it.

As Sulfur (S) is less electronegative than oxygen (O) so, an S-atom is placed at the center of the [SO₃]^2- Lewis structure while the three O-atoms are placed in their surroundings, as shown below.

3. Connect outer atoms with the central atom

At this step of drawing the Lewis structure of a molecule or molecular ion, we need to connect the outer atoms with the central atom using single straight lines. As the O-atoms are the outer atoms in the Lewis structure of the sulfite [SO₃]^2- ion so all 3 oxygen atoms are joined to the central S-atom using straight lines, as shown below.

Each straight line represents a single covalent bond containing 2 electrons.

Now, if we count the total valence electrons used till this step out of the 26 available initially, there are a total of 3 single bonds in the structure above. Thus, 3(2) = 6 valence electrons are used till step 3.

Total valence electrons available – electrons used tillstep 3 = 26-6 = 20 valence electrons.
This means we still have 20 valence electrons to be accommodated in the Lewis dot structure of [SO₃]^2-.

4. Complete the octet of outer atoms

There are three O-atoms present as outer atoms in the Lewis structure of [SO₃]^2-. Each O-atom needs a total of 8 valence electrons in order to achieve a stable octet electronic configuration.

Each S-O bond already represents 2 electrons therefore all the three O-atoms require 6 more electrons each to complete their octet. Thus, these 6 valence electrons are placed as 3 lone pairs on each O-atom, as shown below.

5. Complete the octet of the central atom

Total valence electrons used tillstep 4= 3 single bonds + 3 (electrons placed around O-atom, shown as dots) = 3(2) +3(6) = 24 valence electrons.
Total valence electrons available – electrons used till step 4 =26-24 = 2 valence electrons.

So, these 2 valence electrons are now placed as a lone pair on the central sulfur atom, as shown below.

The structure above shows that there are a total of 3 single bonds and 1 lone pair on the central S-atom which makes a total of 8 valence electrons in its surroundings. Thus, the central S atom as well as all the three O atoms now have a complete octet electronic configuration.

But, the thing is, is this Lewis structure stable? Let’s check that using the formal charge concept.

6. Check the stability of the SO₃^2-Lewis structure using the formal charge concept

The less the formal charge on the atoms of a molecule, the better the stability of its Lewis structure.

The formal charge can be calculated using the formula given below.

Formal charge = [ valence electrons – nonbonding electrons- ½ (bonding electrons)]

Now let us use this formula and the Lewis structure obtained in step 5 to determine the formal charges on a sulfite [SO₃]^2- ion.

For sulfur atom

Valence electrons of sulfur = 6
Bonding electrons = 3 single bonds = 3(2) = 6 electrons
Non-bonding electrons = 1 lone pair = 2 electrons
Formal charge = 6-2-6/2 = 6-2-3 = 6-5 = +1

For oxygen atom

Valence electrons of oxygen = 6
Bonding electrons = 1 single bond = 2 electrons
Non-bonding electrons = 3 lone pairs = 3(2) = 6 electrons
Formal charge = 6-6-2/2 = 6-6-1 = 6-7 = -1

This calculation shows that a +1 formal charge is present on the central Sulfur atom and a -1 formal charge is present on each of the three oxygen (O) atoms.

But as we already mentioned; the fewer the formal charges on the bonded atom, the greater the stability of a Lewis structure.

Thus, we can reduce the formal charges present on the S and O-atoms by converting the lone pair of electrons present on any one terminal O-atom into a covalent bond between the central S atom and the terminal O-atom.

Let us see how that’s done.

7. Minimize the formal charges on atoms by converting lone pairs into covalent bonds

One lone pair from any one terminal oxygen atom is converted into a covalent bond between the central S-atom and the respective O-atom as shown below.

Now there are a total of 2 single bonds and 1 double bond around the central S-atom. We can again check the stability of this Lewis structure using the formal charge formula.

For sulfur atom

Valence electrons of sulfur = 6
Bonding electrons = 1 double bond + 2 single bonds = 1(4) + 2(2) = 8 electrons
Non-bonding electrons = 1 lone pair = 2 electrons
Formal charge = 6-2-8/2 = 6-2-4 = 6-6 = 0

For double-bonded oxygen atom

Valence electrons of oxygen = 6
Bonding electrons = 1 double bond = 4 electrons
Non-bonding electrons = 2 lone pairs = 2(2) = 4 electrons
Formal charge = 6-4-4/2 = 6-4-2 = 6-6 = 0

For single-bonded oxygen atoms

Valence electrons of oxygen = 6
Bonding electrons = 1 single bond = 2 electrons
Non-bonding electrons = 3 lone pairs = 3(2) = 6 electrons
Formal charge = 6-6-2/2 = 6-6-1 = 6-7 = -1

So here, you can see that the formal charges present on the central sulfur (S) atom and a terminal oxygen (O) atom are reduced to zero. However, there is a -1 formal charge on each of the other two oxygen atoms.

-1 + (-1) = -2 which accounts for an overall negative 2 charge on the sulfite [SO₃]^2- ion. This ensures that it is a correct and stable Lewis representation for the sulfite [SO₃]^2- ion. The [SO₃]^2- Lewis structure is enclosed in square brackets and a negative 2 charge is placed at the top right corner, as shown below.

If you are worried about the extra 2 electrons in the sulfur atom which means more than the octet number of electrons. Then, that’s not a problem because sulfur (S) has an expanded octet. It can accommodate more than 8 valence electrons during chemical bond formation due to the presence of a 3d subshell in its atomic structure.

Another interesting fact to keep in mind is that the actual structure of a sulfite [SO₃]^2- ion is a hybrid of the following resonance structures. Each resonance structure is a way of representing the Lewis structure of a molecule or an ion.

These resonance structures show that the formal charges present on [SO₃]^2- atoms are not stationary, rather they keep moving from one position to another. Similarly, a double bond can be formed between the central sulfur and any one terminal oxygen atom out of all the three available.

In conclusion, all the above resonance structures contribute equally to the resonance hybrid which is the best possible Lewis structure of the sulfite [SO₃]^2- ion.

Now, that we have discussed everything about the Lewis structure of [SO₃]^2-, let us proceed forward to the next section of the article.

Also check –
How to draw a lewis structure?
Formal charge calculator
Lewis structure calculator

The sulfite [SO₃]^2- ion has a trigonal pyramidal shape and molecular geometry while the ideal electron pair geometry of the ion is tetrahedral. There is a lone pair of electrons present on the central S-atom in [SO₃]^2-.

The lone pair-bond pair electronic repulsions distort the geometry and shape of the molecular ion and make it adopt a different shape from its electronic geometry.

Molecular geometry of [SO₃]^2-

The sulfite [SO₃]^2- ion has a trigonal pyramidal molecular geometry and shape. There is a lone pair of electrons present on the central sulfur atom in sulfite. Therefore, lone pair-bond pair electronic repulsions exist in the molecule in addition to bond pair-bond pair repulsions.

This repulsive effect distorts the shape of the molecule and makes it adopt a trigonal pyramidal shape. The lone pair is situated at the apex of a pyramid that has a triangular base, as shown below.

An important point to note is that the molecular geometry or shape of a molecule or a molecular ion strongly depends on the different number of bond pairs and lone pairs present on the central atom.

However, the ideal electron pair geometry only depends on the total number of electron pairs present on the central atom, no matter whether it’s a bond pair or a lone pair.

Let us see how this concept is applied to the sulfite [SO₃]^2- ion.

Electron geometry of [SO₃]^2-

According to the valence shell electron pair repulsion (VSEPR) theory of chemical bonding, the ideal electron geometry of a molecule or a molecular ion containing a total of 4 electron density regions around the central atom is tetrahedral.

In the sulfite [SO₃]^2- ion, there are 2 single bonds, 1 double bond and 1 lone pair on the central sulfur atom which makes a total of 4 electron density regions. Thus it has a tetrahedral electron pair geometry.

An easy way to find the shape and geometry of the molecule is to use the AXN method.

AXN is a simple formula to represent the number of atoms bonded to the central atom in a molecule and the number of lone pairs present on it.

It is used to predict the geometry or shape of a molecule using the VSEPR concept.

AXN notation for [SO₃]^2- molecular ion

A in the AXN formula represents the central atom. In the [SO₃]^2-ion, sulfur is present at the center so A = Sulfur.
X denotes the atoms bonded to the central atom. In [SO₃]^2-, three oxygen (O) atoms are bonded to the central S so X=3.
N stands for the lone pairs present on the central atom. As per the Lewis structure of [SO₃]^2-there is one lone pair on central sulfur so N=1.

So, the AXN generic formula for the [SO₃]^2- ion is AX₃N.

Now, you may have a look at the VSEPR chart below.

According to the VSEPR chart given above, the ideal electron geometry of a molecule or a molecular ion having AX₃N generic formula is tetrahedral while its molecular geometry or shape is trigonal pyramidal, as we already noted down for the [SO₃]^2- ion.

Hybridization of [SO₃]^2-

The sulfite [SO₃]^2- ion has sp³ hybridization.

The electronic configuration of a sulfur (S) atom is 1s² 2s² 2p⁶ 3s² 3p⁴.

The electronic configuration of oxygen (O) atom is 1s² 2s² 2p⁴.

During chemical bonding, the paired 3p electrons of sulfur get unpaired and one of these electrons shifts to an empty 3d atomic orbital of sulfur. Consequently, the 3s orbital hybridizes with three 3p orbitals to yield four sp³ hybrid orbitals. Each sp³ hybrid orbital has a 25 % s-character and a 75% p-character.

Three of the four sp³ hybrid orbitals contain a single electron each while the fourth sp³hybrid orbital contains paired electrons. These paired electrons are situated as a lone pair on the central S atom in the sulfite [SO₃]^2- ion.

The two sp³ hybrid orbitals containing single electrons form S-O sigma (σ) bonds with the p orbitals of oxygen by sp³-p overlap, on each side of the [SO₃]^2- ion.

The remaining sp³hybrid orbital of sulfur forms a sigma (σ) bond with an sp² hybrid orbital of oxygen in the S=O double bond.

The unhybridized d orbital of sulfur overlaps with the unhybridized p orbital of this oxygen to form the required pi (π) bond in the S=O double bond of the sulfite ion.

Refer to the figure given below for understanding these concepts more clearly.

A shortcut to finding the hybridization present in a molecule or a molecular ion is by using its steric number against the table given below. The steric number of central S in [SO₃]^2- is 4 so it has sp³hybridization.

Steric number	Hybridization
2	sp
3	sp²
4	sp³
5	sp³d
6	sp³d²

The steric number of central Sulfur in SO₃^2- is 4 so it has sp³hybridization.

The SO₃^2-bond angle

The ideal bond angle in a tetrahedral molecule is 109.5° but in the sulfite [SO₃]^2- ion, the lone pair present on the central sulfur atom distorts the shape and geometry of the molecular ion. It adopts a triangular pyramidal shape and consequently, the O-S-O bond angle decreases from the ideal 109.5° to approx. 106°.

Although a S=O bond is expected to be stronger and shorter in length than an S-O bond. But, experimental results reveal that it is due to the resonance present in the sulfite ion that all three S-O bond lengths in [SO₃]^2- are equivalent and equal to 151 pm.

Also check:-How to find bond angle?