# What is the effective nuclear charge in hydrogen atom?

In hydrogen atom, there is only one electron. Hence, there is no electron shielding at all. That means the shielding constant $S = 0$, and so:
${Z}_{\text{eff}} = Z - {\cancel{S}}^{0}$
and the effective nuclear charge is ${Z}_{\text{eff}} = Z = 1$, where $Z$ is the atomic number.