(1) Upto 14 electrons, molecular orbital configuration is ->


N_b = No of electrons in bonding molecular orbital

N_a $$=$$ No of electrons in anti bonding molecular orbital

Here N_a = Anti bonding electron $$=$$ 4 and N_b = 10

(2) After 14 electrons to 20 electrons molecular orbital configuration is ->



Here N_a = 10

and N_b = 10

Now from question, in F atom 9 electrons present, so in F₂, 9 $$ \times $$ 2 = 18 electrons present.

Molecular orbital configuration of F₂(18 electrons) is

$${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,{\sigma _{2{s^2}}}\,\sigma _{2{s^2}}^ * \,{\sigma _{2p_z^2}}\,{\pi _{2p_x^2}}\, = \,{\pi _{2p_y^2}}\,\pi _{2p_x^2}^ * \, = \,\pi _{2p_y^2}^ * $$