How does effective nuclear charge (Zeff) affect atomic size?

Effective nuclear charge increases from left to right across a period and therefore the atomic radius decreases.

As we go across a period the atomic size decreases due to Effective nuclear charge increases by 0.65 in the ##2^(nd)## and the ##3^(rd)## period But for the d block it's 0.15 .

Hope this helps! :)