Test 1

How are elements heavier than iron produced? 
Elements heavier than iron are produced in stellar interiors via neutron capture. During stellar nucleosynthesis, a nucleus captures a neutron, which increases the atomic mass by one. If the newly formed nucleus is stable, it will remain an isotope of that element. If not, the atom β-decays and becomes an isotope of the next heavier element. In the s-process, nuclides capture neutrons slowly compared to β-decay. On the other hand, if nuclides capture neutrons quickly compared to β-decay, this process is called the r-process. Nuclides will continue to capture neutrons, and when successful, evolve to heavier elements until they reach a size that they undergo fission (whose smaller nuclei can now capture free neutrons) or the neutrons run out.