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Why the bond angle of ammonia is less than 109° 28` ? Give reason.

Why the bond angle of ammonia is less than 109° 28` ? Give reason.

Grade:11

2 Answers

Aamina
64 Points
7 years ago
  • Ammonia has four groups of electrons and so it has the same electronic geometry as other molecules like CH4. 
  • In case of NH3 however, one group has an unshared pair of electrons, and as per VSEPR the four electron groups around a central atom will be directed towards the corners of tetrahedron to give maximum separation. 
  • N has tetrahedral electronic geometry, which refers to the geometric arrangement of electron groups around central atom. 
  • The molecular geometry however excludes the lone pairs on the central atom and describes only the arrangement of atoms around the central atom.
  • Ammonia (NH3) is an example of molecule in which the central atom has both shared and unshared electron pairs. The shape of ammonia molecule (NH3) is trigonal pyramid.
  • There are three bonding pairs of electrons and one non bonding pair. The bond angle in a molecule of ammonia are 107o, a value very close to tetrahedral angle (109o.5').
  • We can write a general tetrahedral structure for the electron pairs of ammonia by placing the non bonding pair at one corner.
  • A tetrahedral arrangement of the electron pairs explains the trigonal pyramidal arrangement of the four atoms.
  • The bond angles are 107o (not 109o.5') because the non bonding pair occupies more space than the bonding pairs.
ankit singh
askIITians Faculty 614 Points
3 years ago
he shape of ammonia molecule (NH3) is trigonal pyramid. ... A tetrahedral arrangement of the electron pairs explains the trigonal pyramidal arrangement of the four atoms. The bond angles are 107o (not 109o. 5') because the non bonding pair occupies more space than the bonding pair

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