Primitive chondrites heated for one week under conditions reasonable for early solar system objects readily lose volatile/mobile trace elements, e.g., Ag, Bi, Cs, Ga, In, Se, Te, Tl and Zn. Trace element contents decrease by 10-100x progressively with temperature up to 1000° C; apparent activation energies calculated from these data suggest bonding differences between chondrites. Comparison of data for E3-6 chondrites and heated Abee (E4) indicates that volatile/mobile trace elements in E-group chondrites reflect metamorphic loss from a parent object; prior nebular cosmochemical fractionation modified non-volatile element contents. Apparently L3-6 chondrites escaped such open-system metamorphism. Information on nebular condensation process(es) may be gained from L-group compositional data; only nonvolatile elements in E-group chondrites should be used for this purpose, however.