through gold and lead, to uranium. Then they will be scattered throughout nearby space. In summary, it has taken three steps to create the chemical elements from which we are constructed. Hydrogen and helium, the simplest atoms in the periodic table, were created during the big bang. In their death throes, medium to large stars create elements such as carbon (6 protons), nitrogen (7 protons), oxygen (8 protons), silicon (14 protons), and up to iron (with 26 protons). As dying stars throw off their outer layers, these elements are scattered through space, which is why, though not as common as hydrogen and helium, these elements are more common than the other elements of the periodic table. The remaining elements were manufactured and scattered through space in supernova explosions. (If you’re wearing a gold ring, it was forged in a supernova and is on very temporary loan to you!) The ¿rst stars provided the energy Àows and the chemical ingredients needed to make even more complex entities such as our Earth. Ŷ
Lecture 8: Threshold 3—Making Chemical Elements
Essential Reading Brown, Big History, chap. 1. Christian, Maps of Time, chap. 2. Delsemme, Our Cosmic Origins, chap. 3.
Supplementary Reading Chaisson, Epic of Evolution, chap. 3. Croswell, The Alchemy of the Heavens.
Questions to Consider 1. What were the three main stages in which the chemical elements were forged?
2. Why are chemical elements crucial to the emergence of new forms of complexity? 40
