Cliffs AP Chemistry, 3rd Edition

(singke) #1
(b) Restatement: The OH bond angle of H 3 O+is less than 109.5°.


  • Lewis structure of H 3 O+:


•H 3 O+is pyramidal in geometry due to a single pair of unshared electrons.


  • Angle of tetrahedron is 109.5°; this exists only if there are no unshared electrons.

  • Repulsion between shared pairs of electrons is less than repulsion between an unshared
    pair and a shared pair. This stronger repulsion found in the shared-unshared pair condi-
    tion, as seen in H 3 O+, decreases the bond angle of the pure tetrahedron (109.5°).
    (c) Restatement: Compare CO bond lengths as found in CO and CO 3 2–

  • Lewis structure of CO:

  • Lewis structures of CO 3 2–

  • CNO–exists in three “resonance” forms. CO bond length is considered to be the average
    of the lengths of all single and double bonds.
    (d) Restatement: CNO–ion is linear.

  • Lewis structure of CNO–:

  • There are no unshared pairs of electrons around the central atom N, resulting in a linear
    molecule.

  • The molecule is polar because O is more electronegative than C.


C N O


O

O O

C

O

O O

C

O

O O

C

2 − 2 − 2 −

CO

H

H
HO

+

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