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.
K is group IA - charge of 2+
Magnesium IIA - charge 2+
Bromine VIIA charge of 1-
Scandium IB
The answer is B
Calculate molar mass first and then calculate moles using this formula:
Moles=given mass/ molr mass
I think it’s found in the nucleus and has a mass of one amu
It would go B. A. E. D. C.
Hope I helped!