Difference between basicity and reducing character My understanding of basicity and reducing character:


Reducing character is the ability of a substance to reduce something else. So it itself must get oxidized. Since $\ce{BiH3}$ has a large radius, it will loose hydrogen atoms easily. Hence I conclude $\ce{BiH3}$ has more reducing character than $\ce{NH3}$.
Basicity is how easily can the compound give up hydrogen atoms/electrons.


Now I end up thinking basicity and reducing character are the same thing. And that $\ce{BiH3}$ should have more basicity than $\ce{NH3}$. But, this is not the corrrect answer.

So what's the difference between reducing character and basicity?

On mostly all Google searches I find that reducing character is directly proportional to basicity. But that doesn't say why they are different in the first place.
Basicity is how easily can the compound give up hydrogen atoms.


Isn't this the definition for acidity instead? (assuming your "hydrogen atoms" = proton) Basicity instead refers to how easily a compound can accept protons on its lone pair, not give them up.

$\ce{BiH3}$ is a weak base, because the lone pair on bismuth is dispersed over a large surface area, as compared to that on the nitrogen in ammonia. (details here) Being diffused, the lone pair is unable to attack a proton, and hence, is a weak base.

$\ce{BiH3}$ is a better reducing agent, because on getting oxidised (losing a hydrogen), the negative charge formed on the bismuth atom is dispersed over a much larger surface area. Hence, the negative charge is stabilized much more on the bismuth atom than it would be stabilized on the nitrogen atom in ammonia.

Notice that the dispersion of the lone pair makes it more diffused, hence, less basic. While dispersion of the excess negative charge stabilizes the specifies formed after loss of a hydrogen, hence, a better reducing agent.