Bromo trifluoride (BrF3) is a highly reactive species and both the Br and F atoms belongs to the halogen group and hence are categorised as interhalogen compounds. In this article we will discuss about the valence electrons, lone pairs, shape etc of BrF3 with the help of Brf3 Lewis structure.
From BrF3 Lewis structure the compound BrF3 is sp3d hybridised and 3 fluorine atoms bonded to Br in T-shaped with two lone pairs of electrons present in central atom Br and have a bond angle about 86.2o. Formal charge of BrF3 zero and are polar in nature.
Brf3 valence electrons
The valence electron number of BrF3 is 28 (7 from Br and 21 electrons from 3 fluorine atoms).
The valence electron number of an atom is 10 minus its group number to which it belongs. Both the Br and F atoms belongs to the 17th group in the periodic table and therefore,
The valence electron number of Br = 17-10 = 7
The valence electron number of F = 17-10 = 7
There are 3 Fluorine atoms in BrF3 so,
The total valence electrons of BrF3 = 7 + 7(3) =7 + 21 =28
How to draw Brf3 lewis structure?
In the BrF3 Lewis structure the central atom Br is bonded to the surrounding 3 fluorine atoms by pairing its valence electrons present in its outermost shell.
1)Know the number of valence electrons of a compound
There are a total of 28 valence electrons present in BrF3 (7 from Br and 21 from 3 fluorine atoms).
2)Choose the least electronegative atom as the central atom and the and place the other atoms surrounding the central atom.
Among the Br and F atoms, Br is less electronegative than F and therefore Br is chosen as the central atom and the 3 fluorine atoms are placed around Br.
3)Pair the valence electrons of central atom and the surrounding atoms to form a single bond between them.
The valence electrons of Br and F are paired and placed in between them
4)The remaining valence electrons are placed around the atoms to complete its octet.
From 28 valence electrons 6 electrons are use for bond formation and now 22 electrons are remaining in which each fluorine atom takes 6 electrons each to complete its octet.
Thus, 3 fluorine atoms take up to 18 electrons from 22 electrons. Now remaining there is only 4 electrons which is placed on the central atom Br and hence Br has 10 electrons (4 nonbonding and 6 bonding) in its outer shell.
Each fluorine atom has 8 electrons (6 nonbonding and 2 bonding electrons) in its valence shell thus completing its octet.
This how BrF3 Lewis structure is drawn.
Brf3 lewis structure lone pairs
In BrF3 the central atom Br has 2 lone pair (4 nonbonding electrons) of electrons present in its outermost shell.
Each fluorine atom has 3 lone pair (6 nonbonding electrons) of electrons and thus a total of 9 lone pair (18 nonbonding electrons) of electrons are present in 3 fluorine atoms.
Brf3 lewis structure octet rule
The central atom Br has 10 electrons in its outermost shell which disrupts the octet rule to have 8 electron configurations.
The central atom Br belongs to the 4th period so their valence shell is composed of 4s, 4p, 4d orbitals in which 4d orbital is empty and can take in more electrons. This is the reason why Br has 10 electrons and thus have an expanded octet.
Brf3 lewis structure formal charge
The formal charge of BrF3 is 0.
Formal charge on an atom in a Lewis structure = total no. 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 = 4
Total number of bonding electrons in bromine atom =6
Formal charge = 7 – 4 – 6/2 =7-4-3 =7-7 = 0
Therefore, the formal charge of bromine atom is = 0
Formal charge on fluorine atom
Total 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 BrF3 will be = 0
BrF3 compound have sp3d hybridisation with 2 lone pair of electrons in the central atom Br.
Electronic configuration of F is [He] 2s2 2p5
Electronic configuration of Br is [Ar] 3d104s2 4p5
Excited state configuration of Br is [Ar] 3d104s2 4p4 4d1
From this above diagram we can see that 3 unpaired (2 in 4p orbital and 1 in 4d orbital) electrons are present in Br excited state.
F atom has 5 electrons in its 2p orbital requires only one electron to complete its octet. So, in the hybridisation state each three F atoms will pair with the 3 unpaired electrons to complete its octet.
This will lead to BrF3 to have sp3d hybridisation.
Brf3 lewis structure shape
BrF3 is sp3d hybridised and so according to VSEPR theory it is a T- shaped compound.
As BrF3 havesp3d hybridisation so they should have a Trigonal bipyramidal geometry but it is a AB3L2 type compound where A is the central atom B is the surrounding atoms and L is the lone pair electrons.
So, due to the presence of 2 lone pair of electrons and its arrangement with the bonded atoms it is T shaped.
Brf3 lewis structure angle
The bond angle of BrF3 Lewis structure is found to be 86.2o less than 90o.
As BrF3 has trigonal bipyramidal geometry the bond angle between the F atoms should be of 90o but due to the presence of 2 lone pair of electrons in Br and the repulsion between the lone pairs will be way higher than from the Br-F bonds and the bond angle will be reduced to 86.2o.
The order of strength of repulsion is;
lp – lone pair
bp – bond pair
Brf3 lewis structure resonance
BrF3 Lewis structure does not have a resonance structure.
The 3 fluorine atoms in BrF3 have complete octet and have no space to accommodate to accommodate more electrons.
For the bromine atom it has 10 electrons in its outer shell so transferring or sharing of electrons between Br-F bond will lead to change the number of electrons other than the 8 electron configuration.
Is Brf3 ionic?
The 3 Br-F bonds in BrF3 is a covalent bond formed by sharing of electrons also there are 2 lone pair of electrons present in Br so it is a covalent compound.
Is Brf3 polar or nonpolar?
BrF3 is a polar compound due to its structure and also electronegativity difference between Br-F bond.
According to VSEPR theory due to the electronic repulsion between the 2 lone pairs and 3 Br-F bond a force will be developed that will push the 3 Br-F bonds downwards causing it to have asymmetry geometry making it polar
The other reason is the net dipole moment of BrF3 is 1.19 D which is non-zero making it a polar compound.
BrF3 compound is soluble in H2SO4 and decomposes on contact with water and organic compounds.
1)Reaction of BrF3 with water;
BrF3 +2H2O –> 3HF + HBR + O2
2) Reaction of BrF3 with organic compound;
BrF3 + CH3CN –> CH3CF3
Is Brf3 acidic or basic?
BrF3 molecule undergo autoionisation
1) Reaction of BrF3 with KF;
KF + BrF3 –> K+ +BrF4 –
Here KF acts as a base and donates F– ion and is easily dissolved in BrF3
2) Reaction of BrF3 with SbF5;
SbF5 + BrF3 –> SbF6 – + BrF2 +
Here SbF5 acts as an acid i.e. the F– acceptor.
With the help of Brf3 Lewis structure we were able to determine valence electrons, lone pair of electrons, hybridization, shape, forma charge, polarity, nature of a compound etc. of Brf3 compound.