Hi, I have a question about this problem. What do you mean by group 1A,3A,5A, etc.? And what do you mean by representative elements?

Representative elements are of s block and p block excluding transition metals and inner transition metals .Groups of representative elements are assigned as 1A (alkali metals ) 2A ....7A (halogens),8A (noble gases).

oh! ok thank you! makes sense now