In the course of his professional career as a scientist, Shahak's work in organic chemistry produced science about organic compounds of the element fluorine (F), contributed to cancer research, for which he gained an international reputation and included posting as an assistant to Ernst David Bergmann, the nuclear physicist who was chairman (1952) of the Israel Atomic Energy Commission (IAEC). In 1961, Shahak pursued post-doctoral studies at Stanford University, in the U.S.; in 1963, he returned to Israel, where he became a popular lecturer and researcher in chemistry, at Hebrew University; moreover, by 1965, Prof. Shahak actively participated in the Israeli politics of the day.