= Solution
Nitrogen-down <adsorption> places the positive hydrogen end farther from the metal, producing an outward molecular <electric dipole moment> and the observed decrease in <work function>. Its maximum normal component, however, is only $1.42$ D. Tilting alone can only reduce that component; it cannot explain an effective $2.20$ D.
The adsorbed <molecule> and metal therefore undergo appreciable <electron density>. Lone-pair donation into the metal, polarization of the substrate, image response and distortion of the adsorbate can change the effective interface dipole. The inferred increase relative to an upright isolated <molecule> is about \b[$0.78$ D]. For scale, transferring about $0.16$ elementary charges over $1$ Å would produce that dipole increment:
$$
\frac{0.78(3.33564\times10^{-30})}{10^{-10}}
\simeq0.16e.
$$
This scale illustrates a plausible interfacial polarization; the work-function measurement alone does not uniquely determine a transferred charge or <adsorption> geometry.
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