Core/shell emulsions with enhanced photographic response

A silver halide photographic element comprises at least one silver halide emulsion layer comprising a silver halide emulsion comprising core/shell silver halide grains wherein the core region comprises silver bromide with from about 5 to about 20% silver iodide and the shell region comprises silver bromide with about 0.1 to about 10% silver iodide and said layer contains a fragmentable electron donor compound of the formula X-Y' or a compound which contains a moiety of the formula -X-Y';whereinX is an electron donor moiety, Y' is a leaving proton H or a leaving group Y, with the proviso that if Y' is a proton, a base, beta-, is covalently linked directly or indirectly to X, and wherein:1) X-Y' has an oxidation potential between 0 and about 1.4 V; and2) the oxidized form of X-Y' undergoes a bond cleavage reaction to give the radical X. and the leaving fragment Y';and, optionally,3) the radical X. has an oxidation potential