What are the observed periodic trends in electron affinity? Check all that apply.
a. For main-group elements, electron affinity generally becomes more negative as you move to the right across a row
b. For main-group elements, electron affinity generally becomes more positive as you move to the right across a row
c. There is not a corresponding trend in electron affinity going right across a row
d. For main-group elements, electron affinity generally becomes more negative as you move down a column
e. For main-group elements, electron affinity generally becomes more positive as you move down a column
f. There is not a corresponding trend in electron affinity going down a column