if the half life of uranium-235 is 7.04x10^8y and 12.5g of uranium-235 remain after 2.84x10^9y how much of the radioactive isotope was in the original sample

In the 1800s, one of the statements in john dalton's atomic theory was that atoms are indivisible. later experimental evidence led to the discovery of subatomic particles such as neutrons, electrons, and protons. what happened to the indivisible atom part of dalton's atomic theory, and why?

Answer explain why it is not possible to deduce a complete order of reactivity.

A1.5l container holds p.50 grams of an unknown gas at a pressure of 0.44 atm and a temperature of 50.c what is the molar mass of the unknown gas