Question

As we know that molecule is a group of atoms but monoatomic consists of one atom(not in group).Why???​

Answer 1

because it's only dependent on valency of that atom that weather it would be mono,di or tri atomic we can predict the structure it'll form by looking at it's valency ..

and the molecule are formed when two or more than two atoms combine .

where as monoatomic are somehow considered to be molecule because it's just because they are independent and are mostly to behave as noble gases .....