4 Groups/Pairs Around the Central Atom

Electron-Pair Geometry

When the central atom has 4 bonding pairs of electron the geometry is tetrahedral. All of the bond angles are 109.5.

When the central atom has 3 bonding pairs of electrons and 1 nonbonding pair the geometry is trigonal pyramidal.

When the central atom has 2 bonding pairs of electrons and 2 nonbonding pair the geometry is bent.

Although bent is used to describe the molecular geometry for a molecule with a central atom having 2 bonding pairs of electrons and 2 non-bonding pairs, it is also used to describe the molecular geometry for a molecule with a central atom having 2 bonding pairs of electrons and 1 nonbonding pair. The difference is in the bond angle.

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