Question

1. write lewis structures for the following molecules or ions, which have central atoms that do not obey the octet rule: 4 a) pf5 b) xef6 c) bh3 d) clf5

Explanation:

Lewis structures show valence electrons as dots/bonds. Central atoms here violate the octet rule (8 valence electrons):

• PF₅: P has 10 valence electrons (5 bonds to F).
• XeF₆: Xe has 14 valence electrons (6 bonds to F + 1 lone pair).
• BH₃: B has 6 valence electrons (3 bonds to H).
• ClF₅: Cl has 12 valence electrons (5 bonds to F + 1 lone pair).

Answer:

a) PF₅: Central P with 5 single bonds to F (each F has 3 lone pairs; P has 10 valence e⁻).
b) XeF₆: Central Xe with 6 single bonds to F and 1 lone pair (each F has 3 lone pairs; Xe has 14 valence e⁻).
c) BH₃: Central B with 3 single bonds to H (no lone pairs on B; B has 6 valence e⁻).
d) ClF₅: Central Cl with 5 single bonds to F and 1 lone pair (each F has 3 lone pairs; Cl has 12 valence e⁻).

(Structures can be represented as:
a) F-P-F (trigonal bipyramidal, all bonds single)
b) Distorted octahedral Xe with 6 F and 1 lone pair
c) Trigonal planar B with 3 H
d) Square pyramidal Cl with 5 F and 1 lone pair)