Sulfur trioxide is a compound with the chemistry formula SO3. This link is of good importance and studied extensively as the reacts v the water existing in the waiting to develop sulfuric acid.

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When this sulfuric acid, in the gas state, mixes v the rain and falls on the Earth, the is dubbed acid rain. The sulfur trioxide is typically colorless and oily however is very corrosive in nature.

Also, that is referred to as battery acid and is supplied to produce acids, fertilizers, lead-acid batteries, in the pickling the metal, purification that petroleum, and also others.

The lewis framework is additionally called an electron dot framework which determines the number of valence electrons existing in an atom.

Moreover, they also describe exactly how these valence electrons are participating in the bond development to type a molecule.

Also, the Lewis framework helps with figuring the end the number and also nature (single, double, and also triple) that the bond displayed with the aid of lines.

This framework is an integral component for anyone that is start to examine atomic chemistry.


To know these diagrams, it is important to know how the number of valence electrons has actually been calculated. The atomic number of the sulfur is 16 which makes its electronic configuration 1s2 2s2 2p6 3s2 3p4.

As the ns shell demands to accommodate 6 electrons, over there is a require for two much more electrons to finish the 3p shell. ~ above the various other hand, the atomic number of oxygen is eight the make its electronic configuration 1s2 2s2 2p4.

Again, there is a require for two an ext electrons to stabilize the 2p shell. Now, the Lewis structure needs to be attracted in together a manner that 3p and also all 2p shells room filled.

Valence Electrons

The electrons the lie in the outermost covering of one atom that conveniently takes component in the bond development are referred to as valence electrons.

The hold of the cell nucleus on these electrons is less in addition to a dearth in number provides these electrons participate in the shortcut formation.

So, in the situation of sulfur trioxide, six valence electrons in every solitary atom the sulfur and also three atom of oxygen take part to form one molecule.

Octet Rule

As per the octet rule, the maximum number of electrons that deserve to be filled in ~ a valence covering is eight.

When they’re much less than eight electrons, just then one atom undergo a bond development either by agree or donating valence electron to attain a stable condition like noble gases.

Both in sulfur and oxygen, over there is a dearth of two valence electron each.

How Sulfur disobey the octet rule?

The catch is in the case of Sulfur i beg your pardon belongs to duration 3 the the regular table.

Sulfur can expand its octet and can accommodate approximately 12 electrons since of which, it does not follow the octet rule.

Sulfur can do so together it has accessibility to energetic 3d-subshell for bonding.

As there is a little energy difference between 3p and 3d shells, v the assist of a little excitation, one unpaired electron can move native the 3p covering to the 3d shell easily.


In case when every the valence electrons room in the 3s and 3p shell, sulfur can develop up come two common covalent bonds and also two lone pairs.

But, once one valence electron reaches 3d shell, sulfur can create four shared covalent bonds and also one lone pair.

It is important to understand that the sulfur can expand its octet to combine a best of ten to twelve electrons.


Moreover, once one much more valence electron reaches the 3d shell, the total number of unpaired electron becomes six in the sulfur.

With this condition, sulfur have the right to now type six covalent bonds permitting twelve electrons roughly its valence shell.

The development of much more covalent bonds means the release of much more energy, permitting the last configuration to be much more stable.


Lewis structure of SO3

The sulfur trioxide is a tetra atomic chemical molecule whereby both the sulfur and three oxygen molecules bond v an equal number of valence electrons.

The diagram is attracted showing dots that valence electrons around the symbol of both sulfur and oxygen atoms v lines predicting link formation.

The Lewis structure of sulfur trioxide (SO3) molecule is drawn by:

First, look for the total variety of valence electrons in a solitary sulfur trioxide (SO3) molecule, i m sorry is twenty-four.

Next, look for just how many much more valence electrons are required to finish all the octet in the sulfur trioxide (SO3) molecule.

It is six for a solitary sulfur trioxide (SO3) molecule, where both sulfur and also each oxygen atom require two valence electron to stabilize their atom.

Next, look because that the number and type of bonds forming within a solitary sulfur trioxide (SO3) molecule. That is three double covalent bonds in between sulfur and oxygen atom each.

Lastly, look for the central atom, which will be sulfur in this case. Finally, draw the skeleton as:


Why SO3 forms double bonds?

Because of same formal charge distribution throughout the atom, twin covalent bonds type in SO3.

It is determined by the variety of electrons one atom lugged – variety of lone pair of electron – fifty percent the number of electrons in bond formation.

So, for oxygen, it is 6-6-1 = -1

And because that sulfur, it is 6-0-3 = +3.

Now, the official charge needs to it is in neutralized to accomplish a steady condition, so having +3 at centre and also -1 in ~ the ends cannot happen. The is the reason why three twin covalent bonds are developed in SO3.

Molecular Geometry of Sulfur Trioxide (SO3)

The over image clears that the shortcut angle amongst oxygen-sulfur-oxygen (O-S-O) atoms have to be much more than 90°.

Moreover, through the valence covering electron pair repulsion (VSEPR) theory, the structure of sulfur trioxide (SO3) is found to it is in bent shaped or trigonal pyramidal or trigonal planar, whereby the bond edge is 120°.

As the equal double bond is formed between each oxygen and a sulfur atom and also no lone pair exists on the central atom (sulfur), there is no distortion in the bond angle what-so-ever.

Moreover, over there is equal charge distribution around the sulfur which is the reason why the sulfur had to expand its octet because that this Lewis framework of SO3.

Therefore, the SO3 molecule turns out to be non-polar in nature. Inspect out the post written on the polarity that SO3.


The Hybridisation that Sulfur Trioxide (SO3)

The hybridization that SO3 is sp2. The is identified with the aid of formula:

Number the hybrid orbitals = variety of sigma bonds + number of lone pairs

In a single shared double covalent bond, over there exists one sigma (σ) bond and one pi (π) bond.

So, the total variety of sigma bonds in a solitary SO3 molecule is three, and also the total variety of lone pairs room 0 (confirm v the Lewis structure).

So, number of hybrid orbitals space 3 + 0 = 3. The is in sp2 hybridization where one s orbital, and two ns orbitals of the exact same shell in ~ an atom overlaps and mixes to develop three new hybrid orbitals of similar energy.

Furthermore, the sp2 hybridization promotes trigonal symmetry through a bond angle of 120°. Moreover, these three brand-new hybrid orbitals have 33.33% features of s orbital and 66.66% features of p orbital.

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The SO3 belongs to period 3 that the routine table in which elements tend to expand their octet and accommodate much more than eight valence electrons. It is amazing to know that this actions is not superior as most facets possess this actions except period two elements. The hybridization in SO3 is sp2 since of the development of one sigma bond and one pi bond.