How to compare electronegativity difference

[Junxi Feng 3B]

For example, between CH4 and CF4, how do you know which one has a greater electronegativity difference by looking at the periodic table? Please be specific on how to get the answer.

What about PH3 and NH3; and SO2 and NO2?

[Amy Luu 2G]

Electronegativity increases as you move to the right and up the periodic table.
For CH4 and CF4, we can compare the electronegativity of H and F. Since F is further to the right than H, its electronegativity is higher (also keep in mind F is known to have a really high electronegativity). Since for both molecules, it is H or F bonded with C, the difference in electronegativity will be dependent on the electronegativity of F and H. Since F has a higher electronegativity than H, CF4 will have the greater electronegativity difference.
For PH3 and NH3, we do the same thing. Since P is below N on the period table, N will have the greater electronegativity and therefore NH3 will have the greater electronegativity difference.
For SO2 and NO2, N has higher electronegativity so NO2 will have greater electronegativity difference.

[LReedy_3C]

You have to use the periodic trend of electronegativity. The trend is the same as ionization energy (growing left to right, bottom to top). Comparing which elements are farther apart will be the way to tell which has the larger electronegativity difference.