The electronic configuration of a dipositive ion $M^{2+}$ is $2, 8, 14$ and its atomic mass is $56$. The number of neutrons in the nucleus would be :

Atomic number means

$Na^{+}$ ion is isoelectronic with

Which of the following has the maximum number of neutrons?

In the two elements, ${ }_{Z_1} A^{M_1}$ and ${ }_{Z_2} B^{M_2}$, the following relations are true. $M_1 \neq M_2$ and $Z_1 \neq Z_2$ but $M_1-Z_1=M_2-Z_2$. These elements are ($M$ is atomic weight, $Z$ is atomic number)

The number of protons,neutrons and electrons in ${ }_{71}^{175} Lu$,respectively,are: