[philonossis]

"Indicate which element or elements have the electron characteristics below. In those cases where a series of elements have the indicated characteristics don't write all the symbols but rather write the atomic numbers of the first and last elements in the series.

(c) Two 7s electrons (note that more than one element qualifies)"

My answer: 88-118 (Those are all the elements to the right of 7s)

Book's answer 88-112.

Question: what doesn't the book include elements 113-115? They are listed in peridic table even though they are unnamed, and they would still have two 7s electrons.

[tamim83]

I suppose it depends on what periodic table you look at.  They can stop listing elements anywhere between 112-118 (usually).  I am not sure which haven't been "confirmed" yet.  Anyhow, you have the right idea and there is nothing wrong with your answer.   

[philonossis]

tamim83:

thank you for responding.