Answer: There is one atom of sulfur and three atoms of oxygen.
Step-by-step explanation:
Sulphur trioxide is a covalent compound because sharing of electrons takes place between sulphur and oxygen. Both the elements are non-metals and hence, will form covalent bond.
The nomenclature of covalent compound is given by:
1. The less electronegative element is written first.
2. The more electronegative element is written then, and a suffix is added with it. The suffix added is '-ide'.
3. If atoms of an element is greater than 1, then prefixes are added which are 'mono' for 1 atom, 'di' for 2 atoms, 'tri' for 3 atoms and so on.
Sulphur trioxide is
and is a compound formed by one atom of sulphur and three atoms of oxygen in a fixed ratio by mass.