Gallium's atomic mass is approximately 69.72 amu, which suggests that the most abundant isotope is likely the one closest to this value. The isotopes of gallium have the following atomic mass numbers:
- Gallium-68 (mass number 68)
- Gallium-69 (mass number 69)
- Gallium-70 (mass number 70)
- Gallium-71 (mass number 71)
Given that the atomic mass of gallium is about 69.72, the most abundant isotope is likely Gallium-69, as it is closest to the average atomic mass.