whats silicons biggest isotope and which one is the smallest?

Answer 1

Naturally occurring isotopes
This table shows information about naturally occuring isotopes, their atomic masses, their natural abundances,
Isotope Atomic mass (ma/u) Natural abundance
28Si 27.9769271 92.2297 percent
29Si 28.9764949 4.6832 percent
30Si 29.9737707 3.0872 percent

Isotopic abundances of Si