This study investigates the surface chemistry and reactivity of magnesium electrodes with various organic solvents to improve understanding of passivation layer formation and its impact on rechargeable magnesium batteries (RMBs). While Mg offers safety and sustainability advantages over lithium due to decreased dendrite formation and higher natural abundance, its performance is hindered by challenges such as passivation layers that impede Mg²⁺ conductivity. Using X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry, we systematically studied Mg reactivity after immersion in ethers, alkyl and cyclic carbonates, esters, and nitriles investigating the composition of the formed passivation layer. With very short immersion, Mg surfaces develop a thin, uneven passivation layer which turns into a more uniform structure over time. Immersion in 0.1 M Mg(TFSI)₂/diglyme electrolyte revealed minimal salt degradation but led to MgCO₃ formation due to salt impurities. Contrary to prior findings, this study demonstrates that the solvent type and immersion duration significantly affect its chemical composition, while the passivation layer thickness increase remains limited upon time of immersion. By providing a detailed quantitative analysis of the Mg passivation process, this work bridges gaps in understanding Mg reactivity with organic solvents and contributes to the development of RMBs.