Answer:
Twice a month, sun and earth are perpendicular
Explanation:
Concentration of Ba2+ is 1.00 mol/dm3 or 1M
I'm pretty sure it's they have the same properties, because they don't have different masses, they don't both have missing nuclei, and they don't hav a different # of protons. Can't recall much else about the two, but I distinctly remember that