Bromo difluoride (BrF2) can be considered as a interhalogen compound. Here we will discuss about the BrF2 Lewis structure and how it helped us to study about its geometry, hybridisation, lone pairs etc.
There are a total of 21 valence electrons in Brf2 Lewis structure in which the central atom bromine (Br) has 9 electrons in its outer shell ie 4 electrons from the bonds formed with 2 fluorine atoms and 5 non bonded (2 lone pairs and one unpaired) electrons. It violates the octet rule.
Brf2 valence electrons
BrF2 compound has 21 odd number valence electrons in its outer most shell.
Bromine and fluorine both belongs to the p block elements and also comes under the 17th group. We know that the valence electron number of an atom will be 10 minus its group number so,
Valence electron of Br = 17-10 = 7
Valence electron of F = 17-10 = 7
Therefore, the total valence electron of BrF2 = 7 + 7(2) =21
How to draw Brf2 Lewis structure?
BrF2 Lewis structure is drawn depending on the valence electrons of Br and F atoms.
1)Know the total number of valence electrons present
Total number of valence electrons present in BrF2 is 21 (7 electrons from bromine and 14 electrons from 2 fluorine atoms).
2)Select the less electronegative atom as the central atom and place the remaining atoms around surrounding the central atom.
Br is less electronegative compared to F atom and hence is selected as the central atom and the 2 fluorine atoms are placed around Br
F Br F
3)Bond the central atom and outer atoms by pairing its valence electrons.
F : Br : F
Among the 21 valence electrons of BrF2 4 valence electrons are used for bond formation between bromine and 2 fluorine atoms so there are remaining 17 non bonded electrons present.
4)The remaining non-bonded electrons are distributed among the atoms to complete its octet.
There are 17 non bonded electrons present and hence each fluorine atoms take 6 electrons each from non-bonded electrons to complete its octet (6 from non-bonded electrons and 2 from single bond formed with bromine). Thus 2 fluorine atoms take 12 nonbonded electrons.
The remaining 5 non bonded electrons are placed on Br atom thus it acquires a total of 9 electrons (5 from nonbonded electrons and 4 from bond formed) as it can have an expanded octet.
Brf2 Lewis structure lone pairs
If we look into central atom Br in the BrF2 Lewis structure it has 5 non bonded electrons in it. It means it has Br has 2 lone pair of electrons and a single unpaired electron
There are 6 non bonded electrons present in each fluorine atom i.e. there are 3 lone pair of electrons present in each fluorine atom.
Brf2 Lewis structure octet rule
BrF2 violate the octet rule of having 8 electrons configuration because the central domain atom Br has 9 electrons in its outermost shell and can have an expanded octet.
The reason is Br atom belongs to the 4th period on the periodic table having n=4 so it has an empty 4d orbital which can accommodate more electrons and can take part in hybridisation.
Brf2 Lewis structure formal charge
Formal charge of Brf2 Lewis structure is zero.
Formal charge on an atom in a Lewis structure = total number of valence electrons in the free atom -the total number of non-bonding (lone pair) electrons -half the total number of bonding electrons.
Formal charge on Bromine atom
Total number of valence electrons in bromine atom = 7
Total number of non-bonding electrons in bromine = 5
Total number of bonding electrons in bromine atom =4
Formal charge = 7-5-4/2 = 7-5-2 =7-7 = 0
Therefore, the formal charge of bromine atom is = 0
Formal charge on fluorine atom
Total number of valence electrons in fluorine atom = 7
Total number of non-bonding electrons in fluorine = 6
Total number of bonding electrons in fluorine atom =2
Formal charge = 7-6-2/2 =7-6-1 =0
Therefore, the formal charge of fluorine atom is = 0
Thus, the total formal charge of the atoms in BrF2 will be = 0
The hybridization state of BrF2 will be determined on the basis of the valence electrons of Br atom and number of fluorine atoms present.
Electronic configuration of F is [He] 2s2 2p5
Electronic configuration of Br is [Ar] 3d10 4s2 4p5
It has a sp3 d hybridization with 2 lone pairs and one unpaired electron The hybridization state of BrF2 compound is highly unstable because there are 3 unpaired electrons present in the excited as we can see from the above diagram and requires 3 electrons to pair with them.
But there are only 2 fluorine atoms in BrF2 which can pair with only 2 electrons leaving one unpaired electron making it highly unstable and logically impossible to exist.
Here the only possible way is it can lose one electron and attain sp3 hybridization with 2 lone pair electrons which will be more stable than BrF2.
It can also either bond with another one fluorine atom and become BrF3 and attain sp3d hybridization with 2 lone pair electrons or gain one electron and become BrF2– with sp3d hybridization having 3 lone pair of electrons.
Brf2 Lewis structure shape
Due to the presence of odd number electrons in the central atom bromine and high repulsion between these 5 nonbonded electrons the shape of BrF2 will be hard to determine.
According to the VSEPR theory steric number is one important factor used to determine the shape of a compound. Let’s say if a compound has steric number 4 then they have tetrahedral or square planar shape and if they have 5 steric number then they have trigonal bipyramidal shape.
But the steric number of BrF2 is found to be 4.5 which is a decimal digit and hence hard to determine its shape.
Brf2 Lewis structure angle
As mentioned above that it was hard to determine the shape of BrF2 due to the presence of odd number of electrons in its central atom having one single unpaired electron making it highly unstable and hence its hard to determine its bond angle as well.
Brf2 Lewis structure resonance
BrF2 Lewis structure does not have a resonance structure the reason is because it has an expanded octet with 9 electrons in its valence shell.
in BrF2 the 2 fluorine atoms have a complete octet and cannot accommodate extra electrons and also for bromine atom it has 9 electrons in its outermost shell due to the presence of empty 4d orbitals and exceed the octet rule to have eight electron configurations.
Having one extra electron than needed so it does not need extra electrons to complete the octet and will not form bond using its lone pair electrons which will increase electron number and hence does not have resonance structure.
Is Brf2 ionic?
BrF2 will be a covalent compound because from its Lewis structure the bond between the Br atom and the 2 fluorine atoms are formed by the sharing of electrons and not by transferring of electrons.
If we also consider the electronegativity of BrF2 the electronegative difference between Br and F is about 1.02 which comes under the covalent character range making it covalent.
Is Brf2 polar or nonpolar?
If we consider the electronegativity of the compound then its value ranges between 2.0 and 0.5 which is a range value for polar covalent compounds making it polar. But it will be hard to determine its polarity without its shape.
But BrF2– is non-polar because of its linear shape. BrF2+ is polar and have bent shape.
Solubility of BrF2 will greatly depend on its polarity and for that shape of the compound is very important as polarity depends on the shape of a compound (substance with same polarities tends to be soluble in one another).
Is Brf2 acidic or basic?
The acidic and basic nature of BrF2 is hard to determine due to the presence of 2 lone pair of electrons and one unpaired electron in its valence shell.
if it loses the lone pair of electrons then will act as Lewis base and if it accepts a pair of electron then will act as Lewis acid.
From the above BrF2 Lewis structure we can say that BrF2 is highly unstable due to the presence of odd number of electrons in the central atom and making it hard to determine its shape also that it violates the octet rule.