Chapter 7: The Origin of Light Elements in the Primeval Fireball

Nuclei, Elements, and Isotopes

An atom’s nucleus will have a definite number of protons and neutrons. Its electrical charge is determined by its number of protons. The atomic number gives the number of protons found in a nucleus, and the mass number gives the number of nucleons- protons and neutrons. However, it turns out that there can be slight variations I elements. These are called isotopes, and they are less common in nature than the element itself. For example, hydrogen has two sister nuclei- the deuterium nucleus and the tritium nucleus. The deuterium nucleus has one proton and one neutron, and the tritium nucleus has one proton and two neutrons. These isotopes are both heavier than hydrogen and less than a fiftieth of a per cent as abundant. The helium nucleus also has two isotopes. The helium has two protons and two neutrons. The isotope, helium-3, has one neutron. There are two heavier nuclei with four and six neutrons, however, these isotopes exist for less than a second.
After counting all of the atoms in the universe, it was found that 99 per cent of them are helium and hydrogen. Helium amounts for about 26 per cent of this total. It is crucial to understand even though there are many heavier elements in the Universe, helium and hydrogen are the most abundant. The origin of helium and hydrogen are crucial to the origin of the other elements found in the Universe.

Synthesizing Helium in the first three minutes of the Universe

Not only does the Universe consist of electrons, protons, neutrons and photons, it is known that the Universe also consists of positrons and neutrinos. Positrons are simply positively charged particles, but neutrinos, like photons, are particles that are almost massless. The number of neutrinos greatly outnumbers the number of protons and neutrons.

Particles are always undergoing transformations or metamorphosis from one particle to another. For example, if a proton collides with the anti-particle of a neutrino, it transforms into a neutron, and it then emits the electron’s anti-particle, the positron. Another reaction can also occur where a neutron collides with a neutrino and creates a proton, whereby releasing an electron. The transformation process is called beta decay. Beta decay, in the early Universe, is responsible for the conversion of protons and neutrons into one another.

The Principle of Thermal Equilibrium is responsible for the variety and proportions o light elements that we see today. The combination and transformations of elements such as hydrogen and helium are responsible for the formation of all the elements. In the early Universe, helium was found. The entire process took just over three minutes, and the result of these collisions was the Universe that we still observe today.