# How do you find number of electrons for Ca^+?

For $C a$ metal, $Z , \text{the atomic number} = 20$.......
If $Z = 20$, by definition, there are $20$ massive, positively charged particles in the calcium nucleus. In the NEUTRAL atom, there must be an equal number of fundamental, negatively-charged particles to balance the positive charge, and these we call electrons.
And thus in a $C {a}^{+}$ atom there are necessarily 19 electrons to account for the charge. How many electrons associated with $C {a}^{2 +}$?