Hydrogen (H) interaction with metals and alloys is of intense interest in a span of topics in materials science and engineering. Distinct H absorption behavior of two similar inter metallic compounds, namely, Zr2Pd and ZrPd2, is not clearly elucidated in terms of their common MoSi2-type structure and hydride-forming constituents. This work addresses that extended structures (electron density topologies) of these compounds are actually different, which causes the different properties they possess. Pseudoatoms manifested by non-nuclear maxima of electron density are uncovered in Zr2Pd's Zr tetrahedral interstices, whereas atoms in ZrPd2 are bonded through straight bond paths. Interstitial pseudoatoms, which are characterized by a weak localization nature revealed by Laplacian calculations, readily lose excess charges to H. Therefore, these properties favor formation of covalent-ionic Zr-H bonding and concurrent H absorption. During Zr2PdH2 formation, the entire topological structure of Zr2Pd is retained; by contrast, ZrPd2H2 formation requires charge redistribution of the stable host lattice of ZrPd2 to change electron density topology and hence is endothermic and unfavorable. The present work reveals a concrete and visualized origin of the distinct H absorption behaviors of the two similar compounds, which has implications in the search for new H-related materials. Copyright (c) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd.-All rights reserved.