David asked in 科學及數學化學 · 1 decade ago

[AL CHEM] Covalent bond --- Bond Angle of H20

Explain why there is a slight increase in the bond angle (H - O - H) in water when the H3O^+ ion is formed.

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  • 1 decade ago
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    圖片參考:http://upload.wikimedia.org/wikipedia/commons/thum...

    Diagram 1: Bond angle representation of water (H2O) [not showing two lone pairs of electron but they should be present]

    圖片參考:http://upload.wikimedia.org/wikipedia/commons/thum...

    Diagram 2: 3-D schematic representation of hydronium ion (H3O+) showing one lone pair of electron

    圖片參考:http://upload.wikimedia.org/wikipedia/commons/thum...

    Diagram 3: 3-D schematic representation of ammonia (NH3) showing one lone pair of electron

    The bond angle (H - O - H) in water is smaller as it has two lone pairs of electrons (not shown in diagrams), which are 'bulky' and forced the H - O - H bond angle to restrain to a smaller angle.

    In the case of hydronium ion, one of the two lone pairs is replaced by a O - H bond, thus leaving one lone pair left, as shown in Diagram 2, making it similar to ammonia in Diagram 3. Less number of 'bulky' lone pairs allow H - O - H bond angle to stretch out to a larger angle, and that is, the slight increase in bond angle mentioned.

    Source(s): http://en.wikipedia.org/ (for diagrams only)
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