How many bonding orbitals are there in #"AsH"_3#?

1 Answer
Aug 15, 2014

There are three bonding orbitals in AsH₃.

If you draw the Lewis structure and the VSEPR shape, you find that AsH₃ has a trigonal pyramidal shape.

The molecule is sp³ hybridized.

There is a lone pair of electrons in one of the sp³ orbitals.

The three As-H σ bonds form by overlapping of the sp³ orbitals with the 1s orbitals of the H atoms.

According to molecular orbital theory, each time you form a bonding σ orbital you also form an antibonding σ* orbital.

So AsH₃ has seven molecular orbitals:

  • 3 bonding As-H σ orbitals
  • the nonbonding sp³ orbital containing the lone pair
  • three antibonding σ* As-H orbitals

The three bonding orbitals and the one nonbonding orbital contain the eight valence electrons in AsH₃.