PPT Slide

34

• The ammonium ion is one of many common  polyatomic ions that have the tetrahedral shape.

• If one of the four electron groups in the tetrahedral  arrangement is a lone pair, the shape is that of a  trigonal pyramid (AX 3E). Example: NH 3.

• As expected, the measured bond angle is slightly  less than the ideal 109.5°.

• If 4 electron groups around the central atom include  2 bonding and 2 nonbonding groups, the molecular  shape is bent (AX 2E 2).

• In H2O molecule, the two lone pairs on the oxygen  atom compress the H–O–H bond angle to 104.5°.

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