No, when a mass of a single element undergoes nuclear fusion, the resulting elements will not necessarily have exactly twice the atomic number of the original element.
Nuclear fusion involves the combination of two or more atomic nuclei to form a heavier nucleus. During fusion, mass is converted into energy according to Einstein's mass-energy equivalence principle (E=mc²). The energy released is crucial for the fusion process to occur successfully.
In fusion reactions, the resulting elements will depend on the specific nuclei involved and the conditions of the fusion process. It is not a guarantee that the newly created elements will have exactly twice the atomic number of the original element.
For example, if hydrogen nuclei (protons) undergo fusion, they can form helium, which has twice the atomic number of hydrogen. However, this is just one example, and there are various fusion reactions with different elements that can result in a range of products with different atomic numbers.
The specific fusion reactions and resulting elements depend on factors such as the reactants, their isotopes, and the conditions of temperature, pressure, and energy involved in the fusion process. Therefore, it is not accurate to assume that all elements produced from nuclear fusion will have exactly twice the atomic number of the original element.