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by ww520 964 days ago
The elemental atoms ultimately came from the inside of the stars.

Hydrogen was created shortly after the Big Bang when the universe had expanded far enough to cool down that protons and electrons could come together to form hydrogens.

Hydrogens come together later to form the stars. Nuclear fusion inside the stars starts due to the pressure from gravity. Nuclear fusion of hydrogens turns them into heliums.

When the hydrogens at the core of the star are used up, the star collapses and then explodes, throwing the upper crust off.

At the core nuclear fusion of heliums starts, forming lithiums. Nuclear fusion of lithium then forms beryllium. The cycles of nuclear fusion of each element type continue to create the heavier and heavier elements. Carbons are created among the way. So is oxygen.

During each cycle the star explodes and throws off the elements from the upper crust.

After iron is created, nuclear fusion stops. Iron is super stable to resist nuclear fusion. Gravity continues to collapse the star until super nova happens.

Super nova is when all the other heavier elements created. Gold, silver, lead, platinum, uranium and others are created during this explosion.

The elements come together to form the planets and eventually become part of us. So we were created long ago inside a star.

2 comments

Nitpicking: Most of the Helium was formed a few minutes after the Big Bang, not inside stars. https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis
Good catch. I basically wrote from memory, on the phone with little verification.
> Iron is super stable to resist nuclear fusion.

Why? What property of 26 protons makes it super stable?

It's the electromagnetic force of their 26 electrons that pushes two iron atoms apart such that the gravitational force of the star cannot overcome.

Nuclear fusion happens when two atoms come close enough that their strong nuclear force binds them together. Strong nuclear force only has effect in very short distance at the nuclear. Smaller atoms with their smaller size allow gravity of the star to push them together for fusion to happen. Bigger atoms with their more numerous electrons make it more difficult.

Bigger stars with stronger gravity can force fusions all the way to iron. Although iron resists fusion, a worse fate awaits it. With no more fusion, the star collapses further and becomes much hotter. The iron nuclei are broken down into alpha particles. The electrons and protons combine to form neutrons, releasing a flood of neutrinos, which cause supernova. Supernova has enough strength to cause fusions of all the heavier elements.

Thank you, this is phrased so well!
Actually I missed one crucial detail. Not just the electrons of the atoms are repelling each other, the positively charged protons of the atoms are repelling each atom as well, even more so. As the protons are tightly packed in the nucleus, it's even more difficult to force the nucleus of two atoms together.