The adiabatic electron affinities of five second row atoms (Al, Si, P, S, Cl) and their monoxides and dioxides were determined using six different density functional or hybrid Hartree-Fock/density functional methods. The 15 species selected form a convenient closed set for which reliable experimental electron affinities exist for 13 of the species. Zero-point vibrational energy corrected electron affinities are also reported. Equilibrium geometries and vibrational frequencies were determined with each density functional method. The method based on the Becke exchange functional and the Lee-Yang-Parr correlation (BLYP) functional reproduced the experimental electron affinities most accurately, having an average absolute error of 0.15 eV. Using this functional, the electron affinities were predicted for SiO and SiO2, molecules for which electron affinities are not known experimentally, as 0.11 eV and 2.03 eV, respectively. It is concluded that the accuracy observed for density functional theory methods applied to first row atoms and molecules extends to molecules containing second row atoms and that density functional theory continues to provide a computationally affordable means of producing electron affinities reliable to within a few tenths of an eV of definitive experimental values.