Bortrifluoreto (BF3) The Lewis structure consists of three B-F bonds, with boron in a central position and all three fluorine as outer atoms in the Lewis diagram. The Lewis dot structure of BF3contains a total of 3 binding pairs and 9 lone pairs.
BF's drawing of the Lewis structure3it's very easy and simple. Let's see how it goes.
Steps to draw Lewis dot structure for BF3
1. Count the total valence electron in BF3
First, determine the available valence electron to draw the Lewis structure of BF3because the Lewis diagram deals with the representation of valence electrons around atoms.
So an easy wayFind the valence electronof non-BF atoms3The molecule must consider only the periodic group of boron and fluorine atoms.
Since the boron atom belongs to the 13th group of the periodic table and fluorine is in the 17th group, the valence electron for boron is 3 and for the fluorine atom it is 7.
⇒ Total number ofValence electrons in boron= 3
⇒ Total number ofValence electrons in fluorine= 7
∴ Total number of valence electrons available for BF3Lewis structure = 3 + 7×3 =24 valence electrons[∴BF3Molecule has one boron atom and three fluorine atoms]
2. Find the least electronegative atom and place it in the middle
An atom with a lower electronegative value is preferred for the central position on the Lewis diagram because it is more apt to share electrons with surrounding atoms.
No case of BF3molecule, the boron atom is less electronegative than the fluorine atom.
Therefore, place the boron atom in the middle position of the Lewis diagram and all three fluorine atoms outside of it.
3. Connect the outer atoms to the central atom with a single bond
In this step, connect all the outer atoms to the central atom with a single bond.
Um, or BF3Molecule, fluorine is the outer atom and boron is the central atom. Therefore, connect them as shown in the figure below.
Count the number of valence electrons used in the above structure. In the above structure, 3 single bonds are used, and a single bond means 2 electrons.
Therefore, in the above structure,(3 × 2) = 6Valence electrons are used to pull the BF out of a total of 24 available valence electrons3Lewis-Structure.
∴ (24 – 6) = 18 valence electrons
So we have 18 more valence electrons.
4. Place the remaining electrons on the outer atom first, completing its octet
First, let's start by placing the remaining valence electrons on the outer atoms. In the case of BF3molecule, fluorine is the outer atom and each of them needs 8 electrons in its valence shell to complete the octet.
Start by placing the remaining electrons as dots on the fluorine atoms until they complete their octet.
Therefore, all fluorine atoms in the above structure have their full octet because they have all 8 electrons (6 electrons shown as dots + 2 electrons in each individual bond) in their outermost shell.
Now count the valence electron in the above structure again.
In the above structure, 18 electrons are represented as dots + three single bonds containing 6 electrons means that a total of 24 valence electrons are used in the above structure.
Then we use all available valence electrons to draw the Lewis structure of BF3.
We no longer have any extra valence electrons and the central boron atom has only 6 electrons (3 single bonds) in its valence shell.
It should be noted that boron is an exception to the octet rule as it can have 8 electrons or less than 8 electrons in the outermost shell for stability. Boron is an exception, as is aluminum, where it can be octet deficient.
Molecules deficient in octets are those molecules that can achieve stability by having less than 8 electrons around the atoms. Some examples - boron, beryllium, aluminum, hydrogen, lithium, helium
Butboron and aluminumare two of the most common elements that fail to complete the octet, as they reach stability with only 6 valence electrons.
Let's check the formal rate of the above structure to make sure it is stable or not.
5. Check stability using a formal charge concept
The lower the formal charge of the atoms, the better the stability of the Lewis diagram.
Calculate the formal charge of an atom. Use the formula given below-
⇒ Formal billing= (valence electrons – non-bonding electrons – 1/2 bonding electrons)
Let's count the formal fee for this4th stepStructure.
for fluorine atom
⇒ valence electrons of fluorine = 7
⇒ Non-bonding electrons in fluorine = 6
⇒ Bonding electrons around fluorine (1 single bond) = 2
∴ (7 – 6 – 2/2) = 0formal charge on fluorine atoms.
for boron atom
⇒ valence electrons of boron = 3
⇒ Nonbonding electrons on boron = 0
⇒ Bonding electrons around boron (3 single bonds) = 6
∴ (3 – 0 – 6/2) = 0Formal charge on the central boron atom.
Lewis structure of boron trifluoride (BF3).
So in the BF above3Lewis dot structure, all atoms acquire zero formal charge. Even though the central boron atom has only 6 instead of 8 electrons in the valence shell, it also receives a formal charge of zero.
We do not need to form multiple bonds and provide the boron atom with 8 electrons in its valence shell.
Boron can achieve stability by having only 6 valence electrons.
Hence the Lewis structure above BF3(boron trifluoride) is the most stable and suitable in nature.
Also check –
- How to draw a Lewis structure?
- formal fee calculator
- Lewis structure calculator
- A molecular geometry of BF3is planar trigonal.
- The boron atom (B) is in the middle and three fluorine atoms (F) at the apex of an equilateral triangle.
- They are all on the same plane.
- Hence the form of BF3is planar trigonal.
The central atom of boron (B) is bonded to three atoms of fluorine (F) and has no lone pairs of electrons. Therefore, there are three regions of electron density (all three are bonding regions) around the central boron atom.
According to the VSEPR theory, the central atom adopts a trigonal planar geometry with three electron density regions. Because the repulsion in pairs of electrons is minimal in this position.
“An electron density band means the group of bonding or non-bonding electrons present around the atom. The single bond, double bond or even triple bond around the atom is counted as a region.”
The pair of electrons around the central boron atom will repel and try to move away from each other, they will occupy the position where the repulsion between them becomes minimal.
According to the VSEPR theory, "the maximum distance that three electron density regions can get produces a geometry called planar trigonal".
"The geometry of the BF3 molecule is 'Trigonal Planar'. "In terms of chemistry, 'Trigonal Planar' is a model with three atoms surrounding an atom in the middle. It's like peripheral atoms all in one plane, as all three are similar with bond angles of 120° in each, making them an equilateral triangle."
We can also find the electronic and molecular geometry of BF3using the AXN method and the VSEPR chart.
AXN is a simple formula representing the number of bonded atoms and lone pairs on the central atom to predict the shape of the molecule using the VSEPR diagram.
AXN notation for BF3Molecule:
- A denotes the central atom, so boron is the central atom in BF3MoleculeA = Wine
- X denotes the atoms bonded to the central atom, boron is bonded to three fluorine atoms. For this reason,X = 3
- N represents the lone pair of electrons on the central atom according to BF3Lewis, the central boron atom does not have a lone pair. Therefore,N = 0
Therefore, the generic AXN formula for the BF3molecule becomesMACHADO3N0ou AX3.
If a molecule gets AX according to the VSEPR diagram3general formula, so its molecular geometry is trigonal planar and the electron's geometry is also trigonal planar.
Therefore, the molecular geometry for BF3is trigonal planar and its electronic geometry is also trigonal planar.
BF hybridization3it's sp2because the steric number of the central boron atom is three.
The formula for calculating the steric number is:
Steric number = (number of atoms bonded to the central atom + lone pair in the central atom)
No case of BF3Molecule, boron is the central atom bonded to the three bonded atoms (fluorine) and has no lone pairs of electrons.
Therefore,(3 + 0) = 3is the steric number of the central boron atom in BF3molecule that gives Sp2hybridization.
The bond angle of BF3
How do we know the molecular geometry of BF3it is trigonal planar, which means that all the atoms are in the same plane. The three B-F connections are arranged in the same plane with a connection angle of 120° to each other.
∴ The bond angle F-B-F in BF3it's 120 degrees.
Also check:-How to find bond angle?