Nuclear Mass and stability. plotting the $Ag$$-109$ Mass parabola putting the Atomic number on the $x-$axis and the Mass of the nuclei on the $y-$axis (calculated as $M=Z{m}_{p}+(A-Z){m}_{n}-B$).

Noticed that even if the $Ag-109(Z=47)$ is the stable element the minimum of the parabola is on $Z=48$. Is that possible?

Noticed that even if the $Ag-109(Z=47)$ is the stable element the minimum of the parabola is on $Z=48$. Is that possible?