Question

Question 4.7 Discuss the shape of the following molecules using the VSEPR model:

BeCl2, BCl3, SiCl4, AsF5, H2S, PH3

Class XI Chemical Bonding and Molecular Structure Page 130

Answer 1

concept :
structure of any atom depends upon number of bond pair and lone pair.
for finding,
bond pair = total number of atoms present in molecule -1 [ ex:-for H2O, bond pair = 3 -1 = 2 ]

lone pair = [sum of number of valance electrons - 2 or 8 ]/2
2 for Be , Li, H like surrounded atom

ex:- BeCl2
number of lone pair = [ 2× 7 + 2 - 8 × 2]/2 = 0
hence, number of lone pair in BeCl2 = 0

after finding lone pair and bond pair , use VSEPR theory . and get structure of any molecule.





now come to the point ,

BeCl2 : - number of bond pair = 2
number of lone pair = [ 2 × 7 + 2 - 2 × 8 ]/2 =0
hence, structure of BeCl2 Like AB. e.g., linear.
Cl : Be : Cl

BCl3 : - number of bond pair = 3
number of lone pair = [ 7 × 3 + 3 - 3 × 8 ]/2 =0
[ because configuration of B = 1s², 2s², 2p¹ hence, number of valance electrons = 3]

hence, structure of BCl3 like AB2 .e.g., trigonal planar.

SiCl4 :- number of bond pair = 4
number of lone pair = [ 4 × 7 + 4 - 4 × 8]/2 =0
hence, bp's = 4 and lp = 0
e.g., structure of SiCl4 is Like AB3 . e.g., tetrahedral.

AsF5 :- number of bond pair = 5
number of lone pair = [5 × 7 + 5 - 5 × 8 ]/2 =0
hence, bp's = 5 and lp = 0
so, structure of AsF5 is like AB4 .e.g., trigonal bipyramidal.

H2S :- number of bond pair = 2
number of lone pair = [ 6 + 2 × 1 - 2 × 2 ]/2 =2
hence , bp's = 2 and lp's = 2
so, structure of H2S is like AB2L2 [ where L shows the lone pair ] hence, structure of H2S is V- shaped.

PH3 :- number of bond pair = 3
number of lone pair = [ 5 + 3 × 1 - 3 × 2 ]/2 = 1
hence, bp's = 3 and lp = 1
so, structure of PH3 is like AB2L .e.g., pyramidal shape.

Answer 2

Answer:

Open the attachment to get the answer.

Explanation: