Chemistry: The Central Science (13th Edition)

Slater's rules reflect more accurately the steady increase in $Z_{eff}$ as we move from left to right in a row in the periodic table.
The increase in $Z_{eff}$ from Si to Cl is $(6.12+)-(4.29+)=1.83$ According to the results in part a), the increase in $Z_{eff}$ is $(7+)-(4+)=3$ According to the results by Slater's rules, the increase in $Z_{eff}$ is $(6.1+)-(4.15+)=1.95$ Therefore, Slater's rules reflect more accurately the steady increase in $Z_{eff}$ as we move from left to right in a row in the periodic table.