Formation of Elements in the Universe

Study Notes

The formation of all naturally occurring elements is a two-stage process:
- Big Bang Nucleosynthesis: Creates light elements (Hydrogen, Helium, Lithium, Beryllium) during the early universe.
- Stellar Nucleosynthesis: Creates heavier elements inside stars.

The early universe was a hot, dense soup of fundamental particles.
Within fractions of a second after the Big Bang, the universe rapidly expanded and cooled.
Quarks combined to form protons and neutrons.
Protons and neutrons combined to form atomic nuclei, mostly Hydrogen and Helium.
Electrons combined with the nuclei to form atoms, mostly Hydrogen and Helium.
These early light elements laid the foundation for all later chemical elements.

Stars are massive balls of hot gas powered by nuclear fusion in their cores.
In these cores, the very high temperatures and pressures allow hydrogen nuclei to fuse into helium nuclei, releasing a large amount of energy.
As stars age and evolve, heavier elements are formed through fusion processes.
These processes continue until heavier elements like silicon and iron are formed.
Heavier elements are created through a different process: neutron capture, where existing nuclei absorb neutrons to create progressively heavier elements.

Nuclear fusion is the process by which lighter elements' nuclei combine to form heavier elements in stars' cores.
This process requires tremendous amounts of energy to overcome the electrostatic repulsion between positively charged nuclei.
This energy is provided by the high temperatures and pressures in the star's core.

Supernovae are massive explosions of stars that occur near the end of a star's life cycle.
Supernovae are the primary source of elements heavier than iron, which cannot be formed through fusion.
These elements are produced by extreme conditions and ejected into space, where they become the building blocks for new stars and planetary systems.

Isotopes are different forms of the same element that have the same number of protons but different numbers of neutrons.
Isotopes have the same atomic number but different atomic mass numbers.

Scientists have also synthesized new elements in laboratories using nuclear reactions.
These reactions involve bombarding existing nuclei with other particles to create new elements.

Nuclear equations represent the changes in nuclei during nuclear reactions.
The sum of the atomic numbers and mass numbers must be the same on both sides of a nuclear equation.
Alpha particles consist of two protons and two neutrons. Identical to helium nuclei.