Electronegativity is going to be one of the most important periodic trends you need to remember when studying organic chemistry. Now, electronegativity itself is just the measurement of an element's ability to attract electrons to itself. And the periodic trend is that electronegativity increases, moving from left to right across a period, and going up a group. So basically, as you're heading towards the top right corner of the periodic table, you would say that your electronegativity increases. Now if we look at the periodic table here, we can see that a vast majority of it is greyed out. For example, here are our noble gases; we don't include them in electronegativity. They don't want to attract electrons to themselves because they're perfect. Inorganic chemistry itself mainly focuses on nonmetals, which is why you can see a lot of the nonmetals here. Now a few select metals are also included because you will see them pop up from time to time within different reactions. Most of the time, they'll be spectator ions, so it's still important to know what their electronegative pattern will be. But just look at these numbers, learn the general trend. Memorizing numbers is not what's most important.

If we look at this example question, it says, "Which of the following represents the most electronegative group 7A element?" So, group 7A are our halogens. So we're looking at these here. If we look at our choices, sulfur and oxygen are not even in group 7A. So they would be out. So who's left? Bromine, iodine, and chlorine. Remember, as we head up a group, our electronegativity increases. Fluorine is not an option, so that's not going to be an answer. So the next one up would be chlorine. That means option D is the correct answer within this example question.