Which pair of atoms has the highest electronegativity difference?
h – s
h – cl
n – h
o – h
c – h

I'll go through them one by one
1) H-S
The electronegativity of Hydrgoen is 2.2, and sulphur is 2.58,
therefore the difference is 0.38 (2.58-2.2=0.38)
2) H-Cl
Hydrogen: 2.2, Chlorine: 3.16
therefore difference is 0.96
3) N-H
Nitrogen: 3.04, Hydrogen: 2.2
therefore difference is 0.84
4) C-H
Carbon: 2.55, hydrogen: 2.2
therefore difference is 0.35

so, the most apparent electronegativity is chlorine, but this could have been done without actually doing the maths. The trend of electronegativty increases across a period and increases up a period due to the strong affinity of the nucleus with bonding electrons. This does not include noble gases though, as they have no charge due to having complete valance shells. The most electronegative element is Fluorine (9), and the least electronegative element (besides noble gases) is Francium (87)