We present a study of a monolayer of ammonia (NH_3) adsorbed on Cu(110) using core level spectroscopies in combination with ab initio calculations based on density functional theory. In particular, x-ray emission spectroscopy has been applied, providing an unsurpassed view of the electronic structure of NH_3 upon adsorption. The saturated NH3 monolayer, \theta~ 0.4 ML, is found to induce strong adsorbate–adsorbate interaction, causing the molecules to tilt on the surface. Based on the angular distribution of the x-ray emission (XE) spectra, we have been able to estimate a mean tilt angle from the surface normal of 40°–45° for the saturated monolayer; the accompanying theoretical calculations for up to three NH3 molecules on a Cu_21 all-electron cluster model support a tilted structure due to adsorbate–adsorbate dipole, and possibly hydrogen bonding, interactions. Since the creation of a core hole on the nitrogen atom site in the intermediate state of the XE process does not affect the symmetry of the molecule, a separation of valence electronic states having mainly e symmetry (N 2pxy) and a_1 symmetry (N 2pz) has been achieved using angle resolved XE measurements. In addition to the electronic states of free NH_3, evidence of new, substrate induced, states has been found, interpreted as ammonia 3a_1/4a_1-Cu 3d valence band hybrids. It is found that back donation into the previously unoccupied ammonia 4a_1 orbital, and a simultaneous 3a_1 donation into the substrate plays an important role in the surface chemical bond.