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interesting chemistry problem

Sambo2

why is the bond angle around the nitrogen atom 109.5 in an octahedral complex but only 107 in ammonia?

Reply 1

willwillwill

the lone pair in the ammonia repels the hydrogen slightly more so decreases the bond angle

Reply 2

MrCynical

I think the usual explanation is that the repulsion between a lone pair and bonding pair is slightly less than that between two bonding pairs. Assuming you don't want to get too much into molecular orbital theory.

Reply 3

charco

Study Forum Helper

Sambo2

why is the bond angle around the nitrogen atom 109.5 in an octahedral complex but only 107 in ammonia?

I can only imagine that you mean an octahedral ammine complex, eg [Ni(NH₃)₆]²⁺

The nitrogen is bonded to four other atoms in which case the bonding pair bonding pair repulsions are all the same. Bond angle of a perfect tetrahedron = 109º 28'