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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: conan741 on April 05, 2010, 06:33:34 PM

Title: Bond angle differences between NH3 and PH3
Post by: conan741 on April 05, 2010, 06:33:34 PM
So I'm trying to figure out the contributing factor to why Azane (Ammonia- NH3) has a larger bond angle of 107.8 compared to Phosphane (Phosphine- PH3) of 93.5.

Here's what I'm thinking: due to the electric moment between the N-H bonds being large it will result in the H being closer to the central atom.  This results in a more tetrahedral angle than say that of PH3 since the electric moment between the P-H bonds is almost non-existent.  

Does this mean that the lone pair in PH3 has a much more dramatic effect on the P-H bonds than the lone pair in NH3?

If the electronegativities between bonding atoms are small will the resultant be a longer bond length?