neon has 3 different isotopes, neon-20, neon-21, and neon-22. the first isotope has a mass 19.992 amu and an abundance of 90.60% . the second isotope (neon-21) has an abundance of 0.21%. the third isotope has a mass 21.991 amu and an abundance of 9.20%. what is the mass of the second isotope?

Which is not true regarding reaction rates? (2 points) catalysts are not used up in the reaction. catalysts speed up reactions by lowering the activation energy. reaction rates decrease as the concentration of reactants decrease. during reactions, concentrations of all reactants decrease at the same rate.