What is the correct formula for calcium fluoride

What did the experiments of scientists after john dalton reveal about his atomic theory?

Boron has an average atomic mass of 10.81. one isotope of boron has a mass of 10.012938 and a relative abundance of 19.80 percent . the other isotope has a relative abundance of 80.20 percent what is the mass of that isotope? report two decimal places

This element is in the same family aa lead and it has fewer protons than sodium.