Explain how to find the combining ratio and chemical formula between calcium and astatine

Sorry i dont understand the question can you rephase it?

Its carbonyl

13 protons and 14 neutrons.  this also means that the amount of electrons also is 13 because electrons have the same amount as protons..the atomic number means the amount of protons (which effectively tells you the electrons) the atomic mass, tells you the amount of protons and neutrons in the nucleus.hope this .