Introduction:
According to molecular orbital theory, the formation of covalent bonds between atoms is explained by the overlapping of atomic orbitals to form molecular orbitals. These molecular orbitals can be classified into two types: sigma (σ) bonds and pi (π) bonds.

F2 Molecule:
F2 is a diatomic molecule composed of two fluorine atoms. Each fluorine atom has 9 electrons, with 1s2 2s2 2p5 electron configuration. When two fluorine atoms come close together to form F2, their atomic orbitals overlap to form molecular orbitals.

Sigma Bond in F2:
A sigma bond (σ bond) is formed by the head-on overlap of atomic orbitals along the internuclear axis. In the case of F2 molecule, the 1s orbitals of the fluorine atoms overlap to form a sigma molecular orbital, known as the sigma bonding orbital (σ1s). This sigma bond holds the two fluorine atoms together.

Pi Bonds in F2:
A pi bond (π bond) is formed by the sideways overlap of atomic orbitals. In the F2 molecule, the 2p orbitals of the fluorine atoms overlap sideways to form two pi molecular orbitals, known as the pi bonding orbitals (π2px and π2py). These pi bonds are formed above and below the internuclear axis.

Summary:
According to the molecular orbital theory, the F2 molecule consists of one sigma bond (σ1s) and two pi bonds (π2px and π2py). The sigma bond is formed by the head-on overlap of the 1s orbitals, while the pi bonds are formed by the sideways overlap of the 2p orbitals. These bonds are responsible for holding the two fluorine atoms together in the F2 molecule.