[leena]

The acidic strength of group5 oxides,
N₂O₃
P₂O₃
As₂O₃
Sb₂O₃
Bi₂O₃
decreases down the group ,similar to the oxides in group 6.

Now for the group 5 hydrides,
NH₃
PH₃
AsH₃
SbH₃
BiH₃
From NH3 to AsH3(from top to bottom),the acidic strength increases whereas from BiH3 to SbH3 (from bottom to top)it's the other way round  the acidic strength increases.
A similar trend is seen in the hydrides of group 6,
From H₂O to H₂Se(downwards)the acidic strength increases whereas from H₂Po to H₂Te(upwards) the acidic strength increases.

My question is,why do the hydrides of group5 and group6 elements behave in this manner of first increasing acidity down the group ,then decreasing acidity down their groups?
And how come the acidic strength of the oxides of the same elements decrease down the group?
Is there a reason for their difference in behaviour ?
I thought of considering the electronegativity difference in the 2 compounds,but it didn't help me understand.

Thanx

[leena]

Ummm... does anyone know why the hidrides behave this way?
or is there no particular reason the hydrides behave like this ?

Any help would be very much appreciated !

[Stephen]

Nice question, I'd like to hear answer too

[Mitch]

I don't have an answer. Do realize though you are trying to compare the acid strength of metal hydrides to that of non-metal hydrides and metalloid hydrides. Weird stuff is bound to happen.