Well, we know there are three strong binary acids, HI, HBR, and HCL, and we still need to know how to compare binary acid strengths. Nonetheless, because you could be asked to compare the strengths of two strong binary acids or to compare the strengths between weak binary acids, how exactly would we do that?
Well, we're going to say here that the strength of binary acids is based on the electronegativity or atomic radius of the non-hydrogen element. So if we take a look at a typical periodic table, we're looking at electronegativity. As we go from left to right on the periodic table, electronegativity, abbreviated EN, would increase. And if we go down any group, we're going to say that atomic radius, abbreviated AR, would also increase.
OK, so these are the directions that allow these two periodic trends to increase. Now how does this relate to the strength of binary acids? We're going to say here when comparing the strengths of binary acids if the elements are in the same row, then use electronegativity to compare their acid strengths. So here we're going to say the greater the electronegativity of the non-hydrogen element, then the more acidic the acid.
If elements are in the same group or column, then use atomic radius in order to compare their acid strengths. Here we're going to say that the greater your atomic radius, then the more acidic your acid, right? So these are the concepts, periodic trends we're going to use to compare the strengths of different binary acids to one another.