Sulfur trioxide is a compound through the chemical formula SO3. This compound is of great importance and also studied extensively as that reacts with the water present in the air to develop sulfuric acid.

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When this sulfuric acid, in the gaseous state, mixes with the rain and also falls ~ above the Earth, it is called acid rain. The sulfur trioxide is normally colorless and also oily yet is highly corrosive in nature.

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

The lewis structure is also called an electron dot framework which identify the number of valence electrons current in an atom.

Moreover, they additionally describe just how these valence electrons space participating in the bond development to kind a molecule.

Also, the Lewis framework helps through figuring the end the number and also nature (single, double, and also triple) of the bond shown with the assist of lines.

This structure is an integral component for anyone who is beginning to research atomic chemistry.


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

As the p shell needs to accommodate 6 electrons, over there is a need for two more electrons to finish the 3p shell. On the other hand, the atomic variety of oxygen is eight that make its digital configuration 1s2 2s2 2p4.

Again, there is a need for two more 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 space filled.

Valence Electrons

The electrons the lie in the outermost shell of one atom that conveniently takes component in the bond development are dubbed valence electrons.

The host of the cell core on this electrons is less in addition to a dearth in number makes these electrons get involved in the link formation.

So, in the situation of sulfur trioxide, six valence electrons in every single atom the sulfur and three atoms of oxygen get involved to type one molecule.

Octet Rule

As every the octet rule, the maximum variety of electrons that have the right to be filled in ~ a valence shell is eight.

When they’re less than eight electrons, only then one atom experience a bond formation either by accepting or donating valence electron to achieve a stable problem like noble gases.

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

How Sulfur disobey the octet rule?

The capture is in the instance of Sulfur which belongs to duration 3 of the routine table.

Sulfur can increase its octet and can accommodate up to 12 electrons because of which, that does not follow the octet rule.

Sulfur deserve to do so together it has access to energetic 3d-subshell for bonding.

As over there is a small energy difference in between 3p and also 3d shells, through the aid of a little excitation, an unpaired electron have the right to move indigenous the 3p covering to the 3d shell easily.


In situation when all the valence electrons space in the 3s and also 3p shell, sulfur can develop up come two mutual covalent bonds and also two lone pairs.

But, as soon as one valence electron get 3d shell, sulfur can develop four mutual covalent bonds and also one lone pair.

It is important to recognize that the sulfur can expand its octet to combine a maximum of ten come twelve electrons.


Moreover, when one an ext valence electron get the 3d shell, the total variety of unpaired electron becomes six in the sulfur.

With this condition, sulfur can now form six covalent bonds permitting twelve electrons approximately its valence shell.

The development of much more covalent bonds way the relax of an ext energy, enabling the last configuration to be much much more stable.


Lewis structure of SO3

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

The diagram is drawn showing dots the valence electrons around the symbol of both sulfur and oxygen atoms with lines predicting shortcut formation.

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

First, look because that the total variety of valence electron in a solitary sulfur trioxide (SO3) molecule, i beg your pardon is twenty-four.

Next, look for how many an ext valence electron are necessary to complete all the octet in the sulfur trioxide (SO3) molecule.

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

Next, look for the number and kind of bonds developing within a single sulfur trioxide (SO3) molecule. It is three dual covalent bonds in between sulfur and also oxygen atom each.

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


Why SO3 forms dual bonds?

Because of equal formal charge circulation throughout the atom, dual covalent bonds type in SO3.

It is figured out by the number of electrons an atom brought – number of lone pair of electrons – half the variety of electrons in shortcut formation.

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

And for sulfur, the is 6-0-3 = +3.

Now, the officially charge requirements to be neutralized to accomplish a stable condition, so having actually +3 in ~ centre and -1 at the ends cannot happen. It is the reason why three double covalent bonds are developed in SO3.

Molecular Geometry that Sulfur Trioxide (SO3)

The over image removes that the link angle amongst oxygen-sulfur-oxygen (O-S-O) atoms need to be more than 90°.

Moreover, with the valence covering electron pair repulsion (VSEPR) theory, the structure of sulfur trioxide (SO3) is uncovered to be bent shame or trigonal pyramidal or trigonal planar, whereby the bond angle is 120°.

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

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

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


The Hybridisation that Sulfur Trioxide (SO3)

The hybridization the SO3 is sp2. It is established with the assist of formula:

Number the hybrid orbitals = number of sigma bond + number of lone pairs

In a solitary shared twin covalent bond, there exists one sigma (σ) bond and also one pi (π) bond.

So, the total number of sigma bond in a single SO3 molecule is three, and the total variety of lone pairs are 0 (confirm through the Lewis structure).

So, variety of hybrid orbitals space 3 + 0 = 3. The is in sp2 hybridization whereby one s orbital, and also two p orbitals the the exact same shell in ~ an atom overlaps and also mixes to create three brand-new hybrid orbitals of comparable energy.

Furthermore, the sp2 hybridization disclosure trigonal symmetry through a bond edge of 120°. Moreover, this three brand-new hybrid orbitals have 33.33% characteristics of s orbital and also 66.66% attributes of p orbital.

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The SO3 belong to duration 3 the the regular table in which elements tend to increase their octet and also accommodate more than eight valence electrons. It is amazing to recognize that this behavior is not outstanding as most facets possess this behavior except duration two elements. The hybridization in SO3 is sp2 due to the fact that of the formation of one sigma bond and also one pi bond.