Question

In ammonia, a central nitrogen atom is bonded to three hydrogen atoms. Similarly, boron trifluoride has a central boron atom bonded to three fluorine atoms. However, ammonia is pyramidal and boron trifluoride is trigonal planar in shape. Which statement justifies this difference in their structure?

Answer 1

The lone pair of electrons on the nitrogen in ammonia decreases the bond angle between the bonding pairs, giving it a pyramidal structure.

Answer 2

Answer is: The lone pair of electrons on the nitrogen in ammonia decreases the bond angle between the bonding pairs, giving it a pyramidal structure.

Electron configuration of nitrogen atom: ₇N 1s² 2s² 2p³.

In ammonia (NH₃), nitrogen atom has five valence electrons with an additional electron from each hydrogen atom, so total number of electrons is eight.

There are three electron pairs used as bond pairs and one lone pair of electrons. The lone pair of electrons repel more strongly than bond pairs, so bond angles are 106.7°.