Answer
The effective nuclear charge for the 2p electrons: $Z_{eff}(F^-)=7+$ and $Z_{eff}(Na^+)=9+$
Work Step by Step
The formula to calculate $Z_{eff}$ for the 2p electrons is $$Z_{eff}=Z-S$$
Z: the nuclear charge of the element
S: the screening constant
Both $F^-$ and $Na^+$ have 10 electrons and the same electron configuration: $1s^22s^22p^6$.
That means for the 2p electrons, both have 2 core electrons and 8 valence electrons.
Therefore, the screening constant $S$ of both $F^-$ and $Na^+$ for the 2p electrons is $$S=2\times1.00+8\times0.00=2.00$$
The nuclear charge of $F^-$ is $Z=9+$
The nuclear charge of $Na^+$ is $Z=11+$
Therefore, the effective nuclear charge of $F^-$ and $Na^+$ is
$Z_{eff}(F^-)=(9+)-2.00=7+$
$Z_{eff}(Na^+)=(11+)-2.00=9+$
