explain bond angle of hydrides of 15 gp. elements

explain bond angle of hydrides of 15 gp. elements


10 Answers

878 Points
13 years ago

Dear amit,

All these hydrides are covalent in nature and have pyramidal structure. These involve sp3 hybridization of the central atom and one of the tetrahedral position is occupied by a lone pair.

Shape of NH3 molecule

Shape of NH3 molecule

Due to the presence of lone pair, the bond angle in NH3 is less than the normal tetrahedral angle. It has been found to be 107o. Down the group the bond angle decreases as:

bond angle of trihydrides


In all these hydrides, four electron pairs, three bond pairs and one lone pair surround the central atom. Now, as we move down the group from N to Bi, the size of the atom goes on increasing and its electronegativity decreases. Consequently, the position of bond pair shifts more and more away from the central atom in moving from NH3 to BiH3. For e.g., the bond pair in NH3 is close to N in N-H bond than the bond pair in P-H bond in PH3. As a result, the force of repulsion between the bonded pair of electrons in NH3 is more than in PH3. In general, the force of repulsion between bonded pairs of electrons decreases as we move from NH3 to BiH3 and therefore, the bond angle also decreases in the same order.

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Sagar Singh

B.Tech IIT Delhi

12 Points
9 years ago
Thank you so much sir awsum explanation 
Himanshu Rajput
26 Points
7 years ago
Among the trihalides of nitrogen which one is most basic A NF3 B NCl3 C NI3 D NBr3 please answer this question
21 Points
7 years ago
I think nitrogen tri fluoride i..e NF3 is more basic among all the halides of nitrogen because it is more elctronegative
13 Points
7 years ago
NI3.>NBr3>NCl3>NF3, Because flurine is most electrogativity than other halide, it will pull electrons towards itself so nirtogen cannot give its lone pair electron freely
Vivek Kumar
24 Points
7 years ago
Enter your answer here...The bond angle is in this order because flourine is more electronegative so it will pull the electron cloud towards itself resulting in less repulsion between two bond and ultimately bond angle decreases
sahabudin ali
36 Points
7 years ago
because flourine is more electronegtivity and it has pull the electron toward itself and then create a lees repulsive bond between two atom and bond angle decreases.
11 Points
6 years ago
Actually the driving force is the lp- bp repulsions.since down the group bp-bp repulsions are already decreasing thus it`s better to minimise the lp- bp repulsions further so bond angle goes on decreasing
108 Points
5 years ago
Thanks for your answers! 
The answer was really helpful! I was searching this answer for everywhere but was unable to find  it.
Yash Chourasiya
askIITians Faculty 256 Points
3 years ago
Dear Student

The hydrides of these group elements are pyramidal in shape with a lone pair of electrons in one of the orbitals. On moving down the group the bond angles gradually decrease due to a decrease in bond pair-bond pair repulsion.

I hope this answer will help you.
Thanks & Regards
Yash Chourasiya

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