After silicon is ground under 1-chlorooctane, 1-bromooctane, or 1-iodooctane, X-ray photoelectron spectroscopy reveals monolayer quantities of carbon on the resulting particles, which have nanometer to micron dimensions. Previously, it had been proposed that monolayer formation from alkyl halides on scribed, and presumably ground, silicon proceeds via a radical mechanism. This paper contains direct chemical evidence for this radical mechanism by showing the expected combination and disproportionation products from alkyl radicals, which had been predicted as intermediates in monolayer formation (Chem. Mater. 2002,14, 27-19). For example, when silicon is ground in a ca. 50:50 mixture of 1-iodoheptane and 1-iodooctane, gas chromatography-mass spectrometry shows the appearance of the expected disproportionation products: 1-heptene, heptane, 1-octene, and octane. In addition, the combination products tetradecane, pentadecane, and hexadecane are also present in a ca. 1:21 ratio, as expected.