F2 bond order: 7 Facts Beginners Should Know !

by

F2 is chemical formula of fluorine molecule, which comes under a homonuclear diatomic molecule in terms of molecular orbital theory.

F2 molecule is consists of two fluorine atoms. Atomic number if F atom is 9. It has electronic configuration 1s2, 2s2, 2p5. Single F atom of F2 molecule has total nine electrons, so the F2 molecule contains total 18 electrons. The F atoms atomic orbitals get mixed with each other to produce molecular orbitals F2 molecule with energy changes in orbitals. In this article, we are learning about F2 bond order.

F2 bond order diagram

In the F2 bond order diagram i.e. the lewis structure of F2 molecule, which is necessary to draw while calculating the bond order of any molecule. The following diagram shows that the F2 molecule consists 2 F atoms and each single F atom has total 9 electrons in its valence shell i.e. total 18 electrons is present in F2 molecule. But only 14 electrons are involved in bonding and sharing electrons with other atoms.

So, in F2 bond order diagram 2 electrons are involved in bonding to form bond pairs between two F atoms (F-F) out of 14 electrons and the remaining 12 electrons becomes lone pair electrons of 3 sets for each F atom. Thus there are total six lone electron pairs in F2 molecule.

MO f2 3
F2 bond order diagram

How to find F2 bond order?

Number of bonding electrons pairs within two atoms are known as bond order. In atoms having covalent bonds for single bond, bond order is 1, for double bond, bond order is 2, for triple bond, bond order is 3 and so on. To find the bond order of any molecule first we have to draw the lewis structure of molecule and then determine the bond type present within the two atoms.

There is a formula to find the bond order as follows:

Bond Order = [number of bonding electrons – number of antibonding electrons] / 2

Bond Order of F2 = [8 – 6] / 2 = 2/2 = 1

So, the bond order of F2 molecule is 1.

Molecular orbital diagram F2 bond order

When two fluorine atoms get involved to form the F2 molecule, the fluorine molecule atomic orbitals are also involved in the formation of F2 molecule. As the F atom has 1s2, 2s2, 2p5 electronic configuration and having total 18 electrons but four electrons from 1s orbital will not get involved in bonding. So, remaining 14 electrons can be accommodated in molecular orbitals.

f2 bond order
Molecular orbital diagram of F2 molecule

Also 2s orbital of both f atoms overlaps to give σ(2s) and σ*(2s) orbitals. Similarly 2pz orbital being at the axis of overlap produces s σ(2pz) and  σ*(2pz) orbitals, while 2px and 2py orbitals being lateral to the overlap axis produces π and π* orbitals. Filling of electrons takes place from the lower energy as from σ(2s) then π* (2s) then σ(2pz) then π(2p) orbitals and finally in π*(2p) orbitals.

So, the electronic configuration of F2 molecule = KK, σ(2s)2, σ*(2s)2, σ(2pz)2, π(2px)2= π(2py)2, π*(2px)2= π*(2py)2

MOT of F2 bond order

Molecular orbital diagram of F2 molecule shows the electronic configuration as σ(2s)2, σ*(2s)2, σ(2pz)2, π(2px)2= π(2py)2, π*(2px)2= π*(2py)2

So, the bonding MO’s of F2 molecule is σ(2s)2, σ(2pz)2, π(2px)2= π(2py)2 = 8

And the antibonding MO’s of F2 molecule is σ*(2s)2, π*(2px)2= π*(2py)2 = 6

The formula for bond order calculation is

Bond Order of F2 molecule = [Nb – Na] / 2 = [8 – 6] / 2 = 2/2 = 1

Nb = no. of bonding electrons

Na = no. of antibonding electrons

As the MOT of F2 bond order shows 1 bond order for F2 molecule which confirms the presence of single covalent bond between two fluorine atoms. Also F2 molecule has even number of electrons, it is diamagnetic in nature.

Bond order of F2-

F2 molecule has total 18 electrons out of which only 14 electrons are involved in molecular bondings. In F2- molecule we have to add one more electron for minus (-) or negative charge on F2- ion, while calculating bond order of F2-.Therefore, the are total number of valence electrons present in the F2- ion are 15.

So, there are 15 total electrons in F2- at single time until we use them. All the orbitals get completely filled rather than the high energy σ(2pz) antibonding orbital. Hence, now the bonding electrons are 8 and antibonding electrons 7. As F2- has odd number of electrons present on it, it is paramagnetic in nature.

Bond order calculation for F2- ion is as follows:

Bond Order of F2- ion = [No. of bonding electrons – No. of antibonding electrons] / 2

Bond Order of F2- ion = [8 – 7] / 2 = 1 / 2 = 0.5

So, the Bond order for F2- ion is 0.5.

Covalent bond in F2 molecule

F2 (fluorine) molecule is a diatomic molecule having two F atoms in it. The bonding in F2 molecule is purely covalent. The F2 molecule is containing only single fluorine – fluorine (F-F) covalent bond. There are three lone electron pairs present on each F atom for sharing or bonding with other elements.

How many orbitals are singly occupied in F2?

The atomic orbitals of two fluorine atoms get mixed with each other, to form molecular orbitals of F2 molecule. As there are total 14 electrons in the molecular orbital diagram of F2 molecule, which are get filled from the lower energy orbitals to higher energy orbitals. Thus, some electrons occupied high energy level orbitals and some are occupied lower energy level orbitals.

In F2 molecule, the molecular orbital diagram shows that all the MO orbitals get filled with double electrons, there are no single occupied electrons in F2 molecule. The highest energy level σ*(2pz) orbital is vacant, as all the electrons get already filled in previous orbitals. Hence, F2 molecule does not have any single occupied orbital.

F2+ bond order and unpaired electrons

F2 molecule has involved total 14 electrons in MO bonding having bond order one, adding one electron to antibonding orbital of F2 molecule creates negative charge on it i.e. F2- ion which has decrease bond order of 0.5. Similarly removing one electron from antibonding orbital of F2 molecule creates positive charge on it i.e. F2+ ion which has increased bond order.

The molecular orbital electronic configuration of F2+ ion is

σ(1s)2, σ*(1s)2, σ(2s)2, σ*(2s)2, σ(2pz)2, π(2px)2= π(2py)2, π*(2px)2= π*(2py)1

Number of bonding electron in F2+ ion is 10. (σ(1s)2, σ(2s)2, σ(2pz)2, π(2px)2= π(2py)2)

Number of antibonding electrons in F2+ ion is 7. (σ*(1s)2, σ*(2s)2, π*(2px)2= π*(2py)1)

Bond order of F2+ ion = [10 – 7] / 2 = 3 / 2 = 1.5

So, the bond order of F2+ ion is 1.5 which is the highest bond order

As the F2+ has an odd number of electron pair, so it has one unshared electron present on it and it is paramagnetic in nature.

Conclusion:

Bond Order of F2 molecule is 1. Molecular orbital electronic configuration of F2 molecule is σ(2s)2, σ*(2s)2, σ(2pz)2, π(2px)2= π(2py)2, π*(2px)2= π*(2py)2 Bond order of F2- ion is 0.5. Bond order of F2+ ion is 1.5. F2 is diamagnetic and F2-, F2+ is paramagnetic.F2 molecule has no unpaired electrons but F2- and F2+ has 1 unpaired electron.