PHYS 1061 Lecture Notes - Lecture 38: Natural Abundance
Document Summary
Lecture - 38: isotopes of an element have same z, differing n, fission of uranium, fission, there are only three known nuclides (arrangements of protons and neutrons) that undergo fission when introduced to a slow (thermal) neutron: 235u has a half-life of 704 million years. 238u has a half-life of 4. 5 billion years (age of earth) Be: no heavy elements were made in the big bang (just h, he, li, and a tiny bit of, stars only make elements as heavy as iron (fe) through natural thermonuclear, heavier elements made in catastrophic supernovae fusion. Massive stars that explode after they"re spent on fusion. 235u and 238u initially had similar abundance: uranium decay, the natural abundance of uranium today suggests that it was created about 6 billion years ago. Assumes 235u and 238u originally equally abundant. Now have 39. 8% of original 238u and 0. 29% of original 235u.
