The philicity indices, omega(N), and omega(+)(S), characterize a charge transfer process occurring at constant spin number, and the spin polarization for a process at constant number of electrons, respectively. These descriptors are explored for a series of substituted C2HSiX silylene isomers (X = F, Cl, Br, H), providing new insights for a comprehensive description of global and local chemical reactivity patterns and halogen substituent effects in these systems. (c) 2006 Elsevier B.V. All rights reserved.