Question

Structure of Fluorine (F₂).

Answer 1

Fluorine (F₂)

Since the atomic orbital configuration of fluorine is 1s², 2s², 2p_x², 2p_y², 2p_z¹, the molecular orbital configuration of its molecule having 18 electrons will be:

σ 1s², σ * 1s², σ 2s², σ * 2s², σ 2p_x², π 2p_y², π 2p_z², π * 2py², π * 2pz².

Hence the number of covalent bonds in fluorine molecule = 1/2 (8 - 6) = 1. The number 1 of the covalent bond may also be achieved in the other way: the bonding effects of the 2s bonding and antibonding orbitals cancel one another, similarly the effects of 2p, and 2p, bonding molecular orbitals cancel the effect of the corresponding antibonding molecular orbitals with the result the fluorine molecule will be having only one σ bond.

It must be noted that the antibonding orbitals decrease the stability of the bond which also explains why nitrogen is more stable than oxygen. Since all the electrons in N₂ and F₂ molecules are paired, these molecules are diamagnetic, while O₂ having two. unpaired electrons, one each in π * 2р_у and π * 2р_z is paramagnetic.

Remember that isoelectronic species (species have same number of electrons) have the same bond order. For example,

(i) He₂⁺ and H₂^- (having 3 electrons) have bond order of +1/2.

(ii) O₂²⁺, N₂, CN^-, CO and NO⁺ (all having 14 electrons) have bond order of 3.

(iii) O₂⁺, NO and N₂^- (all having 15 electrons) have bond order of 2.5.