Question

Why is BeCl2 linear whereas SnCl2 an angular molecule.

pls. this is urgent.

Answer 1

It is due to the hybridization pattern, 

Actually in case of BeCl2 , 

Total no. of valence electron = 2 (for Be) + 7x 2 ( for Cl) = 16

Bond pair = 2

No. of electrons used in forming the octets and duet = 8 x2 = 16

So, lone pair = 0 

hence, hybridization = sp and shape = linear 

While in case of SnCl2 , 

Total no. of valence electron = 4 (for Sn) + 7x 2 ( for Cl) = 18

Bond pair = 2

No. of electrons used in forming the octets and duet = 8 x2 = 16

So, lone pair = 1

hence, hybridization = sp  but, shape for the molecule changes to angular i.e. V-shaped(due to one lone pair).

I hope it helps u dear.......

Answer 2

☆☆ranshsangwan☆☆

Using the concept of hybridization it can be explained.
Shortcut formula to find hybridization(let X) is-
   X=SA +1/2 * (G-V+/- a)
here, SA=surrounding atoms
G=ground state valency of central atom
V=valency of central atom in given species
+/-a=charge on given species
If X=2 --> sp hybridised
   X=3 --> sp² hybridised
   X=4 --> sp³ hybridised

   X=5 --> sp³d hybridised 
and so on....
So,
Using this formula,
BeCl2 is sp hybridised, so it has linear geometry
and SCl2 is sp³ hybridised, so it has tetrahedron geometry, having angle 109.5°!