The radioisotope gallium-68 is used in nuclear medicine as a traceable radioactive emitter for diagnostic imaging procedures. The ⁶⁸Ga isotope is generated from ⁶⁸Ge by:

Question

Quizplus · Accepted Answer

11ecba2d_11ff_e3f7_a3bf_3b001d7fcc7b_MD0008_00 Radioactive beta decay can occur in three forms: β⁻ decay (electron emission), β⁺ decay (positron emission), and electron capture. In all three forms of beta decay, the mass number remains unchanged whereas the atomic number either increases (β⁻ decay) or decreases (β⁺ decay and electron capture) by 1. As the atomic number changes, the identity of the element changes accordingly. During electron capture, a nuclear proton captures an inner electron near the nucleus and then converts to a neutron. This decreases the atomic number by 1 but leaves the mass number the same. In the conversion of ⁶⁸Ge into ⁶⁸Ga, the identity of the element changes; therefore, the number of protons (atomic number) must decrease by 1. Because the mass number of 68 is unchanged, the loss of 1 proton must then be accompanied by the gain of 1 neutron. Therefore, ⁶⁸Ga is generated from ⁶⁸Ge by converting a proton to a neutron (as occurs during electron capture). (Choice A) Adding a proton to the ⁶⁸Ge nucleus would increase the mass number by 1 and change its identity to arsenic to give ⁶⁹As instead of ⁶⁸Ga. (Choice C) Converting a neutron to a proton in the ⁶⁸Ge nucleus by β⁻ decay leaves the mass number unchanged, but the atomic number would still increase by 1 and change the identity of the isotope to ⁶⁸As. (Choice D) Removing three electrons from ⁶⁸Ge would only produce a ⁶⁸Ge³⁺ ion. It would not alter the nucleus (number of protons) and would not change the identity of the element from ⁶⁸Ge to ⁶⁸Ga. Educational objective: Nuclear conversions may change the atomic number (number of protons) or the mass number (combined number of protons and neutrons). In beta decay, a proton can convert to a neutron (or vice versa), leaving the mass number unchanged.

The Radioisotope Gallium-68 Is Used in Nuclear Medicine as a Traceable