Question

The core of the 40 calcium atom, the most common isotope is symbolized by ₂₀⁴⁰Ca.

Answer 1

1) 20 protons, 20 electrons, 20 neutrons and so 40 nucleons

2) 40 x 1,67 x 10^-27 = 6.68 x 10^-26

This is the core's mass and the atom mass at the same time because the elctron's mass isn't important ( like 1/1000 of the mass )

3) ₂₀⁴²Ca        ₂₀⁴³Ca         ₂₀⁴⁴Ca

Those are the three one's.

4) It forms a cation.