The shielding of electrons gives rise to an effective nuclear charge, zeff, which explains why boron is larger than oxygen. estimate the approximate zeff felt by a valence electron of boron and oxygen, respectively?

The solution would be like this for this specific problem:

 (atomic number) - (core electrons) 

Boron:

Atomic number: 5 
Core electrons: 2

Boron will have the following: 2 core electrons and 3 valence electrons.
(atomic number) - (core electrons)> (5) - (2) = +3 

Oxygen: 
Atomic number: 8 
Core electrons: 2 

Boron will have the following: 2 core electrons and 6 valence electrons. 
(atomic number) - (core electrons)> (8) - (2) = +6 |

So the answer would be +3 and +6.

I hope this helps and if you have any further questions, please don’t hesitate to ask again. 

the ratio of the conjugate base to the acid required to attain the desired ph.