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? view available hint(s) the shielding of electrons gives rise to an effective nuclear charge, , which explains why boron is larger than oxygen. estimate the approximate felt by a valence electron of boron and oxygen, respectively? +5 and +8 +3 and +6 +5 and +6 +3 and +8 +1 and +4