Ready to learn how to draw the lewis structure of PF2- ion?
Here, I have explained 6 simple steps to draw the lewis dot structure of PF2- ion (along with images).
So, if you are ready to go with these 6 simple steps, then let’s dive right into it!
Lewis structure of PF2- ion contains a single bond between the Phosphorus (P) atom and Fluorine (F) atoms. The Phosphorus atom (P) is at the center and it is surrounded by 2 Fluorine atoms (F). The Phosphorus atom has 2 lone pairs, and both the Fluorine atom has 3 lone pairs. The Phosphorus atom has -1 formal charge.
Let’s draw and understand this lewis dot structure step by step.
(Note: Take a pen and paper with you and try to draw this lewis structure along with me. I am sure you will definitely learn how to draw lewis structure of PF2- ion).
6 Steps to Draw the Lewis Structure of PF2- ion
Step #1: Calculate the total number of valence electrons
Here, the given ion is PF2- ion. In order to draw the lewis structure of PF2- ion, first of all you have to find the total number of valence electrons present in the PF2- ion.
(Valence electrons are the number of electrons present in the outermost shell of an atom).
So, let’s calculate this first.
Calculation of valence electrons in PF2- ion
- For Phosphorus:
Phosphorus is a group 15 element on the periodic table.
Hence, the valence electrons present in phosphorus is 5 (see below image).
- For Fluorine:
Fluorine is a group 17 element on the periodic table.
Hence, the valence electrons present in fluorine is 7 (see below image).
Hence in a PF2- ion,
Valence electrons given by Phosphorus (P) atom = 5
Valence electrons given by each Fluorine (F) atom = 7
Electron due to -1 charge, 1 more electron is added
So, total number of Valence electrons in PF2- ion = 5 + 7(2) + 1 = 20
Step #2: Select the center atom
While selecting the atom, always put the least electronegative atom at the center.
(Remember: Fluorine is the most electronegative element on the periodic table and the electronegativity decreases as we move right to left in the periodic table as well as top to bottom in the periodic table).
Here in the PF2 molecule, if we compare the phosphorus atom (P) and fluorine atom (F), then the phosphorus is less electronegative than fluorine.
So, phosphorus should be placed in the center and the remaining 2 fluorine atoms will surround it.
Step #3: Put two electrons between the atoms to represent a chemical bond
Now in the above sketch of PF2 molecule, put the two electrons (i.e electron pair) between each phosphorus atom and fluorine atom to represent a chemical bond between them.
These pairs of electrons present between the Phosphorus (P) and Fluorine (F) atoms form a chemical bond, which bonds the phosphorus and fluorine atoms with each other in a PF2 molecule.
Step #4: Complete the octet (or duplet) on outside atoms. If the valence electrons are left, then put the valence electrons pair on the central atom
Don’t worry, I’ll explain!
In the Lewis structure of PF2, the outer atoms are fluorine atoms.
So now, you have to complete the octet on these fluorine atoms (because fluorine requires 8 electrons to have a complete outer shell).
Now, you can see in the above image that all the fluorine atoms form an octet.
Also, only 16 valence electrons of PF2 molecule are used in the above structure.
But there are total 20 valence electrons in PF2 molecule (as calculated in step #1).
So the number of electrons left to be kept on the central atom = 20 – 16 = 4.
So let’s keep these four electrons (i.e 2 electron pairs) on the central atom.
Now, let’s move to the next step.
Step #5: Check whether the central atom has octet or not. If it does not have an octet, then move the electron pair from the outer atom to form a double bond or triple bond
In this step, we have to check whether the central atom (i.e phosphorus) has an octet or not.
In simple words, we have to check whether the central Phosphorus (P) atom is having 8 electrons or not.
As you can see from the above image, the central atom (i.e phosphorus), has 8 electrons. So it fulfills the octet rule and the phosphorus atom is stable.
Step #6: Final step – Check the stability of lewis structure by calculating the formal charge on each atom
Now, you have come to the final step and here you have to check the formal charge on phosphorus atom (P) as well as each fluorine atom (F).
For that, you need to remember the formula of formal charge;
Formal charge = Valence electrons – Nonbonding electrons – (Bonding electrons)/2
- For Phosphorus:
Valence electron = 5 (as it is in group 15)
Nonbonding electrons = 4
Bonding electrons = 4
- For Fluorine:
Valence electron = 7 (as it is in group 17)
Nonbonding electrons = 6
Bonding electrons = 2
|Formal charge||=||Valence electrons||–||Nonbonding electrons||–||(Bonding electrons)/2|
Let’s keep these charges on the atoms in the above lewis structure of PF2- ion.
As you can see in the above sketch, there is one -ve charge on the phosphorus atom, which indicates the -1 formal charge on the PF2 molecule.
Hence, the above lewis structure of PF2- ion is the stable lewis structure.
Each electron pair (:) in the lewis dot structure of PF2- ion represents the single bond ( | ). So the above lewis dot structure of PF2- ion can also be represented as shown below.