Our universe is a romantic world, those shining stars are like "elemental processing plants", they generate new elements at the same time and constantly shine, and at the end of life, they throw the various elements they have created in their lives into all corners of the universe, and these elements constitute everything in the universe through incomparably exquisite arrangements and combinations, including us humans.
The process of star formation elements is probably like this, the lighter elements are generated by round after round of nuclear fusion reactions inside the star, each round of nuclear fusion will produce heavier elements, and to ignite the next round of nuclear fusion, it will require a higher temperature, if the mass of the star is large enough, the fusion reaction will continue until the formation of iron.
After that, massive stars erupt into powerful supernova explosions, releasing temperatures of up to 100 billion K, in the process, the nuclei of lighter elements are captured through neutrons to generate a large number of heavy elements, and all the natural elements in the universe are generated since then.
After knowing the process of stellar element formation, we seem to have found a law, that is, the formation of elements is closely related to the level of temperature, which is manifested in the need for higher temperatures to form heavier elements. In other words, in an environment with extremely high temperatures, it seems that all elements can be generated.
According to the mainstream view in the modern universe, the "Big Bang" theory describes that the temperature at the birth of the universe was as high as 10^32K, and its temperature was 10 trillion billion times higher than that of supernovae! Now the question arises: if the universe was born at such a high temperature, why didn't the Big Bang generate all the elements in one go?
To figure this out, we need only briefly review the process of the Big Bang.
Because atoms are made of protons, neutrons, and electrons, our discussion can only proceed after all of these particles have appeared. According to theoretical deduction, electrons were generated 10^-35 seconds after the Big Bang, and neutrons and protons did not begin to appear until 10^-12 seconds after the Big Bang, and the temperature at this time has dropped from 10^32K to 10^15K.
Although all the particles needed to make up atoms have appeared, they cannot form atoms at this time because the temperature is too high at this time. The essence of temperature is the intensity of the movement of microscopic particles, at a high temperature of 10^15K, even the strongest force in the universe, the strong interaction force, cannot bind the protons and neutrons moving at high speed.
The temperature after the Big Bang dropped very rapidly, and after 10 seconds, the temperature of the universe had dropped to about 3 billion K, the power of the strong interaction force began to appear, and the nuclear fusion we expected began. However, at this time, the temperature and density of the universe no longer support the formation of those heavy elements, so the nuclear fusion reaction in this time period can only generate some simple atomic nuclei.
This "good time" did not last long, and after about 35 minutes, the temperature of the universe had dropped to about 300 million K, and the universe at this time generated helium, 0.01% of the mass of the universe, and 10^-10% lithium through nuclear fusion reactions. After that, all fusion reactions ceased, and it was not until much, long, long after the birth of the first star that the fusion reactions re-ignited.
The above is the reason why the Big Bang did not generate all the elements in one breath, seeing here, some people may ask, in the process of the Big Bang, why did not appear like supernovae, generated by neutron capture of heavy elements? This is because neutron capture will only occur when the nucleus is large enough, for example, the nucleus of iron-56 that can be captured by neutrons has 26 protons and 30 neutrons, and through the previous introduction, we already know that such nuclei can not be generated at the beginning of the Big Bang.