I am confused about this problem. Any help is appreciated.

Question

A chemist performs a series of reactions that produce binary lithium compounds. The elements include sulfur, chlorine, nitrogen, fluorine, selenium, oxygen, and iodine. The models below represent the ionic radii of compounds formed by reacting lithium with three of the elements.
a. Identify the three compounds that the models represent. Explain your answer. (2 points)

b. Write a hypothesis that the chemist might use when investigating another periodic trend of various elements. (2 points)

Here is the link to the models:

h ttps://www.google.com/search?q=solve:+6,+a+chemist+performs+a+series+of&safe=active&rlz=1C1CHBF_enUS720US720&sxsrf=ALeKk00zUK1oEC7s3gmwrAq4p1i1eFBuhw:1586638197227&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjBuofxn-HoAhUbK80KHY5OAp4Q_AUoAnoECAkQBA&biw=1366&bih=625#imgrc=QWTearlz5AjDdM

Answer 1

Make sure do delete the space between h and t when copying it and pasting it into the search. I did that because jiskha doesn't allow URLs.