Atoms with the same number of protons, but different numbers of neutrons are isotopes of the same element.
Simple!
Atomic number= number of protons AND number of electrons (in an atom)
Mass number= number of neutrons
It B I just took the test ;)
First find the mass
44.1 ml @ 1.55 g/mL = 68.355 grams of Ca
the equation
Ca + O2 → CaO
= 55 grams of O2
