They have the most moons because they have the most mass
The molecular mass of carbon monoxide (CO) is 28 g/mol
<u><em>calculation</em></u>
The molecular mass of CO = atomic mass of C + atomic mass of O
From periodic table the atomic mass of C = 12 g/mol and for O = 16 g/mol
Therefore the molecular mass of Co = 12 g/mol + 16 g/mol = 28 g/mol
It means it depends on how much of the chemical you have. For ex. if 1 drop of snake venom might not kill you, but 20 drop could definitely kill you. Hope this helps!