Among the following pairs of orbitals,which orbital will experience the larger effective nuclear charge?
$(i)$ $2s$ and $3s$
$(ii)$ $4d$ and $4f$
$(iii)$ $3d$ and $3p$

(A) The effective nuclear charge $(Z_{eff})$ experienced by an electron depends on its distance from the nucleus and the shielding effect. Orbitals closer to the nucleus experience a greater effective nuclear charge.
$(i)$ For $2s$ and $3s$,$2s$ is closer to the nucleus than $3s$,so $2s$ experiences a larger $Z_{eff}$.
$(ii)$ For $4d$ and $4f$,$4d$ is closer to the nucleus than $4f$ due to the poor shielding of $f$-orbitals,so $4d$ experiences a larger $Z_{eff}$.
$(iii)$ For $3d$ and $3p$,$3p$ is closer to the nucleus than $3d$,so $3p$ experiences a larger $Z_{eff}$.
Thus,the orbitals experiencing larger effective nuclear charge are $2s$,$4d$,and $3p$.