Electronegativity is a measure of the ability of an atom to attract electrons towards itself. The greater the electronegativity difference between two atoms, the more polar the bond between them. In this case, the electronegativity difference is 3.1 - 0.9 = 2.2, which is quite large. This means that the bond between these elements is likely to be highly polar, with the electrons being pulled towards the more electronegative atom.
