In this article, we should learn about BrO3- lewis structure, shape, geometry, bond angle, and many more detailed facts.
In the BrO3- lewis structure molecule is trigonal pyramidal but due to lone pair geometry is tetrahedral. The central Br atom sp3 hybridized with bond angle 1040 slightly deviated due to the repulsion of the lone pairs. Three Oxygen atoms bind with Br via a double bond or one can bind a single bond only.
Bromate is an oxoanion of Br. The Br-O bond length is around 165 pm and the molecule is asymmetric so it has some dipole moment and it is a polar molecule.
Some important facts about BrO3-
Bromine gas is converted to bromate via the photoactivation process. But in the laboratory bromate can be prepared by dissolving bromine into a concentrated solution of potassium hydroxide solution.
Br + 2 OH– = BrO– + H2O
3BrO– = BrO– + 2Br–
The main process of formation of bromate is a reaction between ozone and bromide.
O3 + Br– = BrO3–
Bromate-containing water is bad for human life.
1. How to draw BrO3- lewis structure?
With the help of lewis structure or lewis dot structure number of electrons participating in bond formation or the number of lone pairs available can predict.
In BrO3- lewis structure, the total electrons involved is 7+ (6*3)+1 = 26 and the electrons needed 8+(8*3)= 32, So the bonding electrons will be 32- 26= 6 electrons and the number of the total bond will be 6/2 =3 bonds.
For drawing BrO3- lewis structure we consider the valence electrons of individually Br as well as Oxygen atoms. Now we have to identify the central atom on the basis of electronegativity. Br is less electronegative than O, so Br will be at the central position and three oxygen atoms are present at three corners.
The molecule is anionic so for one negative charge one electron should be added and from the above calculation we can say that in the molecule there will be a minimum of three sigma bonds should be present. Sometimes two oxygen atoms are connected via a double bond and one lone pair over Br.
2. BrO3- lewis structure shape
The total electron density of the molecule is present over the central Br atom.
In BrO3- lewis structure the geometry of the molecule is trigonal pyramidal but the shape is tetrahedral along with lone pairs. Due to the repulsion of the lone pairs, the bond angle has deviated and there will be two O atoms connected via a double bond.
3. BrO3- valence electrons
In the Bro3- lewis structure the central Br atoms attached double bond with two Oxygen atoms and via single bond with another oxygen atom and containing one pair of lone pair.
The electronic configuration of Br is [Ar]3d104s24p5 and the for O is [He]2s22p4. So, there are 7 and 6 electrons present in the valence shell for Br and O respectively. One negative charge is present in one of the Oxygen atoms so one electron should be added.
So, the total valence electrons for bromate is 7+ (6*3)+1 = 26
4. BrO3- lewis structure formal charge
The formal charge is a hypothetical concept assuming the same electronegativity for all atoms and can calculate the charge accumulate.
The formula we can use to calculate the formal charge, F.C. = Nv – Nl.p. -1/2 Nb.p.
Where Nv is the number of electrons in the valence shell or outermost orbital, Nl.p is the number of electrons in the lone pair, and Nb.p is the total number of electrons that are involved in the bond formation only.
In the BrO3- lewis structure we can see that there are two types of Oxygen present one is bonding via a single bond only other bonding single bonds as well as double bonds. So, the formal charges are different for two types of oxygen atoms.
F.C. of Br is = 7-2-(10/2)=0
F.C. of O (single bond) = 6-6-(2/2)= -1
F.C. of O (double bond) = 6-4-(4/2) =0
So, the formal charge of the single bond containing Oxygen atoms is -1. As the molecule is charged so it has a formal charge too.
5. BrO3- lewis structure lone pairs
The electrons present in the valence shell of an atom in a molecule but do not participate in the bond formation are called lone pairs.
In the BrO3- lewis structure, both Br and O are p block elements so their outermost orbital is P.
Br is VIIA and O is a VIA element so they have seven and six electrons in their valence shell respectively. In the bond formation out of seven electrons, Br used five electrons and two electrons are reminded as lone pair.
For Oxygen atoms out of six electrons, two electrons are involved for one sigma and one π bond, so the rest of the four electrons are present as two pairs of lone pairs. But one oxygen atom formed only a sigma bond and a negative charge is present over it. Here six electrons are not involved in bond formation so here the number of lone pairs is 3.
So, the total number of lone pairs available in bromate is 1+(2*2)+3=8 pairs of lone pairs
6. BrO3- lewis structure octet rule
Every atom in a molecule tries to complete its valence shell by donating or accepting a suitable number of electrons and gaining the nearest noble gas configuration for stabilization.
In the BrO3- lewis structure, there are three sigma bonds present and for each bond two electrons are involved one from Bromine and one from O. Br has one pair of lone pair also. To complete an octet Br can form a bond with three oxygen atoms.
Again, Oxygen has six electrons in its valence shell, so they form a double bond with Br and four electrons are present as lone pair. So, this way they complete their octet. But for one single oxygen atom only form a single bond with Br and bears a negative charge on it to complete its octet.
7. BrO3- lewis structure bond angle
In a particular molecule, all the atoms make a particular bond angle after the formation of the bond for perfect alignment.
In the BrO3- lewis structure, geometry is tetrahedral along with one lone pair present over Br. From VSEPR (Valence Shell Electrons Pair Repulsion) theory a molecule having tetrahedral geometry the ideal bond angle is around 109.50 but here O-Br-O bond angle is 104.070. So, it deviated from its ideality.
There are one lone pair over Br and two lone pairs over O atoms. So, there is massive lone pairs repulsion and to minimize the repulsion the molecule aligns the bond angle reduce to 104.070.
Again, due to the electronegativity of the three oxygen atoms they pull the electron density toward them and the molecule is bent and the angle will be changed.
8. BrO3- lewis structure resonance
Delocalization of electrons clouds in the same molecule but in a different skeleton.
In the BrO3- lewis structure, there are four resonance structures skeleton possible. The structure I, II, and III are equivalent, and structure IV is different from them.
The most contributing structure is structure IV as it contains a higher number of covalent bonds and electronegative atom Br gets a negative charge as well. So, it has more contribution to the resonance structure.
9. BrO3- hybridization
By this hypothetical concept, two different orbitals of different energy undergo mixing and form a new hybrid orbital to form a stable covalent bond.
For bromate ion hybridization is calculated by the formula,
H = 0.5(V+M-C+A), where H= hybridization value, V is the number of valence electrons in the central atom, M = monovalent atoms surrounded, C=no. of cation, A=no. of the anion.
In the BrO3- lewis structure the valence electrons for Br involved in the bond formation (only sigma bond) is 3, one lone pair and the surrounding atom will be 3. The negative charge is on the O atom only so we will not consider it in hybridization.
So, the mode of hybridization of central Br is = ½(5+3+0+0)=4 (sp3)
| Structure | Hybridization value | State of hybridization of central atom | Bond angle |
| Linear | 2 | sp /sd / pd | 1800 |
| Planner trigonal | 3 | sp2 | 1200 |
| Tetrahedral | 4 | sd3/ sp3 | 109.50 |
| Trigonal bipyramidal | 5 | sp3d/dsp3 | 900 (axial), 1200(equatorial) |
| Octahedral | 6 | sp3d2/ d2sp3 | 900 |
| Pentagonal bipyramidal | 7 | sp3d3/d3sp3 | 900,720 |
From the above table, we can be told that if the hybridization value is 4 for any molecule then the molecule is sp3 hybridized. Where lone pairs present as s orbital and three p orbitals are involved in bond formation with three oxygen atoms.
From the box diagram of BrO3- lewis structure it is evident that we cannot consider the π bond in hybridization. Only sigma bonds are involved.
For Br, there are five electrons in the 4p orbital in the ground state and two electrons are transferred in the 4d orbital, and two electrons are present in the 4s orbital as lone pairs. The three unpaired electrons in the 4p orbital now combine with three oxygen atoms to form three new hybrid sigma bonds along with one lone pair.
So here one s and three p orbitals are involved in the hybridization to form an sp3 hybrid orbital. By the mixing of orbital both Br and O can complete their octet.
According to VSEPR theory and the table of hybridization, we can say a molecule having tetrahedral geometry the bond angle will be 109.50, but here the scenario is different due to lone pairs repulsion which is present at the sp3 hybrid orbital.
10. BrO3- solubility
The solubility of any molecule depends on the temperature and nature of the solution and solute also.
In the BrO3- lewis structure, as we can see that bromate is an anion so it is surely soluble in water by the hydration effect. The counter cation of it can attract the bromate molecule and helps the solubility.
It is also soluble in ammonia but insoluble in methanol.
11. Is BrO3- ionic?
According to Fajan’s rule, every molecule has some ionic as well as covalent character.
From the BrO3- lewis structure it is evident that there is a negative charge over the molecule so the molecule possesses some ionic character and it can be ionizable in a particular solution in water. Even Br has some ionic potential but it has less tendency to polarize the small size of oxygen atom as the size of Br is large.
Again, due to the small size of Oxygen, it is less polarizable but the ionic potential of oxygen is high due to its negative charge on it. So, it has some ionic character along with the covalent character.
12. Is BrO3- acidic or basic?
Bromate is a conjugate base of Bromic acid.
From the BrO3- lewis structure we can say that it is the anion of any other salt of any molecule. The counter cation of bromate will be Na+, K+, and H+. Apart from H+, other cations will form a neutral salt with bromate anion.
But when it is attached to H+ then it will form bromic acid (HBrO3). Which is a moderate acid and bromate is its conjugate base.
13. Is BrO3- polar or nonpolar?
Bromate is an asymmetric molecule so it has a resultant dipole moment.
By the value of dipole moment, a molecule can be decided whether is it polar or nonpolar. From the BrO3- lewis structure we can see that it is a tetrahedral shape which is an asymmetric molecule and it has some resultant dipole moment.
The dipole moment acts from Br to O as it is work from less electronegative to more electronegative substituents.
From this structure, it is evident that there is some resultant dipole moment present. So, the molecule is polar in nature.
Summary
From the above discussion of Bro3- lewis structure we can conclude with a few things being tetrahedral geometry but the bond angle is lesser than expected due to the lone pair repulsion. The molecule is a conjugate base of the acid, due to its asymmetric shape, it is polar.
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Hi……I am Biswarup Chandra Dey, I have completed my Master’s in Chemistry from the Central University of Punjab. My area of specialization is Inorganic Chemistry. Chemistry is not all about reading line by line and memorizing, it is a concept to understand in an easy way and here I am sharing with you the concept about chemistry which I learn because knowledge is worth to share it.