This paper presents density functional theory (DFT) calculations for the adsorption energies of hydrogen-containing molecules (CHx, NHx, OHx, SHx) on various transition-metal surfaces. The study finds that the adsorption energy of these molecules scales approximately with the adsorption energy of their central atom (C, N, O, or S), with the scaling constant depending only on the number of hydrogen atoms (x). A model is proposed to explain this behavior, showing that the adsorption energy depends on the valency of the molecule and the properties of the d electrons of the surface. The model is developed into a general framework for estimating reaction energies for hydrogenation and dehydrogenation reactions. The study involves close-packed and stepped surfaces of fcc(111), fcc(100), hcp(0001), bcc(110), fcc(211), and bcc(210). Each surface is modeled with a (2×2) or (1×2) unit cell, and the slabs are three layers thick. The adsorbates and topmost layer are allowed to relax fully, with spin polarization considered for Fe, Ni, and Co. The RPBE functional is used to describe exchange and correlation effects. The results show that the adsorption energy of molecule AHx is linearly correlated with the adsorption energy of atom A: ΔE^AHx = γΔE^A + ξ. The slope γ is given by (x_max - x)/x_max, where x_max is the maximum number of H atoms that can bond to the central atom. This indicates that the slope only depends on the valency of the adsorbate. The d-band model is used to explain the scaling behavior, showing that the coupling to the d states scales with the valency of the adsorbate. The model is tested against full DFT calculations for reactions of hydrocarbons, alcohols, thiols, and amino acids, showing good agreement. The model can be used to estimate reaction energies for hydrogenation and dehydrogenation reactions of organic molecules on transition-metal surfaces. The model is also generalized to use the adsorption energy of any hydrogenated species as a reference. The model is shown to be useful for screening new catalysts and can be combined with Brønsted-Evans-Polanyi-type correlations to estimate the full potential energy diagram for surface catalyzed reactions.This paper presents density functional theory (DFT) calculations for the adsorption energies of hydrogen-containing molecules (CHx, NHx, OHx, SHx) on various transition-metal surfaces. The study finds that the adsorption energy of these molecules scales approximately with the adsorption energy of their central atom (C, N, O, or S), with the scaling constant depending only on the number of hydrogen atoms (x). A model is proposed to explain this behavior, showing that the adsorption energy depends on the valency of the molecule and the properties of the d electrons of the surface. The model is developed into a general framework for estimating reaction energies for hydrogenation and dehydrogenation reactions. The study involves close-packed and stepped surfaces of fcc(111), fcc(100), hcp(0001), bcc(110), fcc(211), and bcc(210). Each surface is modeled with a (2×2) or (1×2) unit cell, and the slabs are three layers thick. The adsorbates and topmost layer are allowed to relax fully, with spin polarization considered for Fe, Ni, and Co. The RPBE functional is used to describe exchange and correlation effects. The results show that the adsorption energy of molecule AHx is linearly correlated with the adsorption energy of atom A: ΔE^AHx = γΔE^A + ξ. The slope γ is given by (x_max - x)/x_max, where x_max is the maximum number of H atoms that can bond to the central atom. This indicates that the slope only depends on the valency of the adsorbate. The d-band model is used to explain the scaling behavior, showing that the coupling to the d states scales with the valency of the adsorbate. The model is tested against full DFT calculations for reactions of hydrocarbons, alcohols, thiols, and amino acids, showing good agreement. The model can be used to estimate reaction energies for hydrogenation and dehydrogenation reactions of organic molecules on transition-metal surfaces. The model is also generalized to use the adsorption energy of any hydrogenated species as a reference. The model is shown to be useful for screening new catalysts and can be combined with Brønsted-Evans-Polanyi-type correlations to estimate the full potential energy diagram for surface catalyzed reactions.