1) s-character tend to concentrate in orbitals that are directed toward electropositive groups and p-character tends to concentrate in orbitals that are directed toward electronegative groups. 2) It can be explained on the basis of Bent's rule. In \\\\(N_{2}F_{4}\\\\), \\\\(N-N\\\\) bond has more s-character, hence, bond length decreases. While in \\\\(N_{2}H_{4}\\\\), \\\\(N-N\\\\) bond has less s-character (i.e. more p-character), hence bond length increases.