Question

Name five atoms and the five colors that describe them?

Answer 1

Order each of the following sets of five atoms and ions according to decreasing size. "1" largest and "5" smallest. 

O 
S^2- 
O^2- 
Te^2- 
Se^2- 

I know the more negative the ion, the larger the element. but i dont understand how to do it when they all have the same charge, and an element with no charge.