Parameter scalings of the core molybdenum (Z = 42) density have been obtained for Alcator C-Mod L- and I-mode plasmas from x-ray observations of the neon-like Mo32+ 4D transition. For Ohmic and ion cyclotron range of frequency (ICRF) L-mode discharges, is found to decrease strongly with increasing electron density ∼1/. For L- and I-mode plasmas, increases roughly quadratically with ICRF power at fixed ne. The outlook for metal content in future devices with ICRF heating is discussed, including estimates for in the Ohmic L-mode target plasmas.