Questions on isotopes.?

1) Because of kinetic isotope effect: due to their larger mes, heavier isotopes tend to react somewhat more slowly than lighter isotopes of the same element. This is most pronounced for protium (1H) and deuterium (2H), because deuterium has twice the m of protium. The m effect between deuterium and the relatively light protium also affects the behavior of their respective chemical bonds, by means of changing the center of gravity (reduced m) of the atomic systems. However, for heavier elements, which have more neutrons than lighter elements, the ratio of the nuclear m to the collective electronic m is far greater, and the relative mass difference between isotopes is much less. For these two reasons, the mass-difference effects on chemistry are usually negligible.