Why are the radii of $_{11}Na$ and $_{20}Ca$ larger compared to $_{12}Mg$?

(N/A) $1$. Across a period from left to right,the effective nuclear charge increases,which causes the atomic and ionic radii to decrease. Since $_{11}Na$ is to the left of $_{12}Mg$ in the same period,$_{11}Na$ has a larger radius than $_{12}Mg$.
$2$. Down a group,the number of shells increases,leading to an increase in atomic and ionic radii. Since $_{20}Ca$ is in the same group as $_{12}Mg$ but is located below it,$_{20}Ca$ has a larger radius than $_{12}Mg$.