How many significant numbers are in 2.03?

2 and 1 are sig figs.

Explanation:

any number that is not zero is a sig fig (exceptions do apply)

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.

it means there are 3 atoms of oxygen