Why is the decrease in atomic size from Lithium to Beryllium much more pronounced than the decrease — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

From $Li$ ($Z=3$) to $Be$ ($Z=4$), the relative increase in nuclear charge is approximately $33\%$. From $K$ ($Z=19$) to $Ca$ ($Z=20$), the relative increase is only around $5\%$. This huge relative percentage jump in the second period causes a much steeper relative contraction in atomic size compared to the 4th period.