Sulfur dibromide (SBr2) lewis dot structure, molecular geometry, bond angle, polar or nonpolar

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SBr2 lewis structure molecular geometry

Sulfur dibromide is a toxic gas with the chemical formula SBr2. It has a molar mass of 191.873 g mol-1

In this article, we will discuss Sulfur dibromide (SBr2) lewis structure, molecular geometry, bond angle, polar or nonpolar, its hybridization, etc.

Sulfur dibromide is prepared by the reaction between sulfur dichloride and hydrogen bromide. 

Name of MoleculeSulfur dibromide
Chemical formulaSBr2
Molecular geometry of SBr2Bent
Electron geometry of SBr2Tetrahedral
HybridizationSp3
NatureSlightly Polar
Bond angleLess than 109.5º
Total Valence electron for SBr220

How to draw lewis structure of SBr2?

SBr2 Lewis structure is made up of two atoms, sulfur, and bromine, the sulfur is in the central position and bromine atoms are in the surrounding position. The lewis structure of SBr2 contains 16 nonbonding electrons and 4 bonding electrons.

The lewis structure of SBr2 is similar to the SCl2 and it is very easy to draw.

Here let’s see how to draw it.

Follow some steps for drawing the lewis dot structure for SBr2

1. Count total valence electron in SBr2

In the very first step, we have to count the number of valence electrons available for drawing the lewis structure of SBr2. For this, we have to count the valence electrons in sulfur and bromine atoms.

The best way to determine the valence electron in an atom is by looking at the group number in the periodic table.

As sulfur atom belongs to group 16th in the periodic table and bromine is situated in 17th group, hence, the valence electron for sulfur is 6 and for bromine atom, it is 7.

⇒ Total number of the valence electrons in sulfur = 6

⇒ Total number of the valence electrons in bromine = 7

∴ Total number of valence electron available for the SBr2 Lewis structure = 6 + 7(2) = 20 valence electrons         [∴SBr2 molecule has one sulfur and two bromine atoms]

Total number of valence electron available for the SBr2 Lewis structure

2. Find the least electronegative atom and place it at center

An atom with a less electronegative value is more preferable for the central position in the lewis diagram because they are more prone to share the electrons with surrounding atoms.

So, in the SBr2 molecule, the electronegativity of sulfur is 2.58 and the electronegativity of bromine is 2.96. Clearly, sulfur is a less electronegative atom.

So, just put the sulfur in the center position and both bromine atoms at the surrounding position.

central atom in sbr2 lewis structure

3. Connect outer atoms to central atom with a single bond

In the third step, draw a single bond to connect both outer atoms (bromine) to the central atom(sulfur).

skeletal structure of sbr2

As in the shown figure, we draw the single bond from the left and right side bromine atoms to the central atom. Now count the valence used in the above structure.

A single bond contains two electrons, and, in the above structure, two single bonds are used, hence, 4 valence electrons are used in the above structure from the total of 20 valence electrons that is available for drawing the lewis structure of SBr2.

∴ (20 – 4) = 16 valence electrons

So, we are left with 16 valence electrons more.

4. Place remaining electrons on outer atoms and complete their octet

In this step, we have to complete the octet of outer atoms first, the octet means having 8 electrons in the valence shell of an atom.

Now in the SBr2 molecule, the bromine is the outer atom and it needs 8 electrons in its valence shell to complete its octet.

So, just start putting the remaining valence electron on bromine atoms till they complete their octet.

Place remaining valence electron in sbr2

So, both bromine atoms in the above structure completed their octet, because both of them have 8 electrons(6 electrons represented as dots + 2 electrons in a single bond) in their valence shell. 

Now again count the total valence electrons used in the above structure.

In the above structure, there are 12 electrons represented as dots + 2 single bonds means 4 electrons are used.

Hence, (12 + 4) = 16 total electrons are used in the above structure from a total of available 20 valence electrons.

Therefore, we are left with 4 more valence electrons.

5. Complete the central atom octet and make multiple bonds if necessary

As we already completed the octet of both bromine atoms, now we have to complete the octet of the central atom which is sulfur in the SBr2 molecule.

In the 4th step structure, we see that the sulfur central atom attached with 2 single bonds means, it has already 4 electrons in its valence shell. Hence, sulfur needs only 4 more electrons to complete its octet

We have 4 remaining valence electrons, hence, put these remaining electrons around the sulfur atom and complete its octet.

SBr2 lewis structure

SBr2 lewis structure

That’s all, we have used all the valence electrons available for drawing the lewis structure of SBr2 and all the atoms in the above structure completed their octet as all of them have 8 electrons in their valence shell.

Now just check the formal charge for the above SBr2 lewis structure.

6. Check the stability with the help of a formal charge concept

The lesser the formal charge on atoms, the better is the stability of the lewis diagram.

To calculate the formal charge on an atom. Use the formula given below-

⇒ Formal charge = (valence electrons – lone pair electrons –  1/2 bonding electrons)

Let’s count the formal charge on the bromine atom first, both bromine atoms in the SBr2 Lewis structure(5th step) have the same bonded pair and lone pair, so, just count the F.C. for the one bromine atom.

For bromine atom:

⇒ Valence electrons of bromine = 7

⇒ Lone pair electrons on bromine= 6

⇒ Bonding electrons around bromine(1 single bond) = 2

∴ (7 – 6 – 2/2) = 0 formal charge on both bromine atoms.

 For sulfur atom

⇒ Valence electrons of sulfur = 6

⇒ Lone pair electrons on sulfur = 4

⇒ Bonding electrons around sulfur (2 single bonds) = 4

∴ (6 – 4 – 4/2) = 0 formal charge on the sulfur central atom.

formal charge in sbr2 lewis structure

So, this is our most stable and appropriate lewis dot structure or electron dot structure of SBr2.

What are the electron and molecular geometry of SBr2?

The molecular geometry of SBr2 is Bent because the central atom sulfur is attached with two bond pairs and there are two lone pairs on it, so, according to the VSEPR theory, these bond pairs and lone pair around the sulfur will repel each other, as a result, they will be pushed apart and pushes down the bonded atoms, giving the shape of SBr2 similar to the bent.

Since the central atom in SBr2 has four regions of electron density(2 bond pairs + 2 lone pairs), its molecular geometry will be bent and its electron geometry will be tetrahedral.

SBr2 molecular geometry or shape

SBr2 molecular geometry

Also, the generic formula for SBr2 is AX2N2 according to the VSEPR theory and its chart.

electron and molecular geometry of SBr2 as per vsepr chart

Hybridization of SBr2

Let’s find the hybridization of SBr2 through the steric number of its central atom.

“Steric number is the addition of a total number of bonded atoms around a central atom and the lone pair present on it.”

∴ Steric number of SBr2 = (Number of bonded atoms attached to sulfur + Lone pair on sulfur)

As per the lewis structure of SBr2, the sulfur atom is bonded with two bromine atoms and it contains two lone pairs of electrons.

∴ Steric number of SBr2 = (2 + 2) = 4

Steric numberHybridization
1S
2Sp
3Sp²
4Sp³
5Sp³d
6Sp³d²

So, for a steric number of four, we get the Sp3 hybridization on the sulfur atom in the SBr2 molecule.

The bond angle of SBr2

The bond angle of SBr2 is less than 109.5º since two lone pairs on the sulfur central atom slightly bring the two bromine atoms closer to each other and make the bond angle less than 109.5º.

Sulfur dibromide polarity: is SBr2 polar or nonpolar?

Is SBr2 polar or non-polar? SBr2 is very slightly polar because of its bent geometrical shape that retains some net dipole moment although the bond(S-Br) is nonpolar because of the very low electronegativity difference between the sulfur and bromine atoms, at last, the polarity in the SBr2 molecule is so low, it can also be considered as nonpolar in nature.

⇒ The electronegativity of bromine = 2.96

⇒ The electronegativity of sulfur = 2.58

∴ The difference of electronegativity between sulfur and bromine = 0.38

According to the Pauling scale, the S-Br bond cannot be polar since the electronegativity difference between them is less than 0.5.

Since the bromine is a little more electronegative than the sulfur atom, a little bit of negative charge will induce on bromine and a little positive charge on sulfur.

Because of this separation of charge, the dipole forms along with the bond and it will not cancel out because of the V-shaped structure of SBr2.

But dipole moment forms in SBr2 is very small because of the very low electronegativity difference between sulfur and bromine.

All this makes, SBr2 slightly polar but the polarity in this molecule is so low, it can also be considered as nonpolar in nature.

FAQ

How many bonding pairs and lone pairs are present in the lewis structure of SBr2?

Bonding pairs are the pair of electrons that are in a bond. A single bond has one bond pair means 2 bonding electrons. 

Lone pairs are those represented as dots in the lewis diagram that do not take part in the formation of bonds and are also called nonbonding electrons.

So, in the SBr2 lewis structure, there are 2 bond pairs means 4 bonding electrons and 8 lone pairs (2 on central atom + 3 on each bromine atom) are present.

Why the molecular geometry of SBr2 is bent but its electron geometry is tetrahedral?

The electron geometry considers both bond pair and lone pair while predicting the geometry of the molecule. And the molecular geometry only considers the bond pair to predict the shape of the molecule.

So, as per the SBr2 lewis structure, the sulfur central atom is surrounded by 4 electron pairs(2 bond pairs + 2 lone pairs).

∴ Four regions of electron density always form a tetrahedral geometry, hence, the electron geometry of SBr2 is tetrahedral.

Summary

  • The total valence electron is available for drawing the SBr2 Lewis structure is 20.
  • The molecular geometry of SBr2 is bent and its electron geometry is tetrahedral.
  • The lewis structure of SBr2 has 4 bonding electrons and 16 nonbonding electrons.
  • The bond angle of SBr2 is less than 109.5º and its hybridization is Sp3.
  • SBr2 is slightly polar, it can also be considered nonpolar because of its very low polarity.
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