13. A radioisotope decays to give a beta particle and oxygen-19. What was the ORIGINAL element? *

You use the atomic number to find out how many protons and neutrons there are in the atom. you use the atomic mass to find out how many protons and electrons there are in the atom. 

Answer(d) unstable compounds that convert to acetals in the presence of alcohol and an acid; (b) semiacetals produced by alcohol subtraction from ketone;