In the 1920s, Hubble was among the first to recognize that there is a universe of galaxies located beyond the boundaries of our Milky Way. During the 1920s, Edwin Hubble observed stars that vary in brightness in a patch of light known at the time as the Andromeda nebula.
Calcium is in group IIA in the periodic table. A Ca ion has a charge of 2+. In order to solve this problem you can either see the periodic table or just look for the charge of the elemetns they give you.
