Our world is a rich tapestry of different compounds, and different elements. How did these basic building block form? The answer varies based on the size of the atom. For brevity's sake, I will not address all of the elements here.
- Hydrogen (atomic number 1) and helium (#2): In Big Bang nucleosynthesis, the Big Bang produced a raw quark-gluon plasma. As the universe cools, this plasma condenses into protons and neutrons. Most of the neutrons decay into protons and electrons, but some bind to protons. As the universe cools further, these one to four nucleon (proton and neutron) elements grab the electrons, forming hydrogen and helium. Very little lithium (#3) and beryllium (#4) was also formed, but atoms so produced were very radioactive and none still exist today.
- Lithium (#3), beryllium (#4), and boron(#5): In addition to creating a quark-gluon plasma, raw energy in the form of light was produced in the Big Bang. This light, called cosmic background radiation, still exists and sometimes slams into atoms. When a carbon atom is slammed into in this way, lithium and beryllium atoms can be formed. Likewise, the same process breaks boron off of oxygen. All of these elements are quite rare.
- Carbon (#6): Once the universe filled with hydrogen and helium gas, gravity began to cause clouds of gas to fall in on itself, forming stars. Stars are, obviously, very hot and very dense. They are hot enough that magnetism no longer is a major force inside of them. They are so dense that sometime three atom nuclei would collide at once. When three helium nuclei collide, carbon is formed. This process is call the triple alpha process, because helium nuclei are sometimes called alpha particles.
- Nitrogen (#7) and oxygen (#8): Once a star begins to fill with carbon, the carbon can be bombarded with protons. As it does, it is converted into nitrogen and oxygen. As a side-effect of these reactions, even more helium is formed, which can form even more carbon via the alpha process. This cycle, called the CNO cycle, is the reason why carbon is the fourth most abundant element in the universe.
- Fluorine (#9): Fluorine is very rare. It is produced in a process similar to the CNO cycle, except that fluorine is almost instantly converted to oxygen and helium, or neon and hydrogen. The only reason why free fluorine exists is because sometimes stars explode before the fluorine has a chance to be destroyed.
- Neon (#10): Neon is produced by fluorine decay. Unlike fluorine, neon is very stable.
