Was the Universe once purely hydrogen?

[Altair33]

From what I’ve read about the formation of stars and heavier elements, stars are formed when hydrogen gas floating around in space clumps together in large enough quantity to cause gravity to create nuclear fusion which turns the hydrogen (with one proton) into helium (with two protons). Furthermore, I’ve read that all the heavier elements- everything “solid” that we see around us, are formed in the larger stars (supernovas) which are able to produce sufficient heat.

Based on the foregoing, is it correct to state that, after the Big Bang, everything was just pure hydrogen?

[wolfstu]

My understanding is that at the initial formation of atoms in the universe, it was mostly hydrogen, with a small but significant fraction of helium, and a small amount of lithium. Everything heavier formed in stellar processes.

From Wikipedia:

Without major changes to the Big Bang theory itself, [Big Bang Nucleosynthesis] will result in mass abundances of about 75% of H-1, about 25% helium-4, about 0.01% of deuterium, trace (on the order of 10[sup]-10[/sup]) amounts of lithium and beryllium, and no other heavy elements.

An alternate source is these lecture notes from the University of Arizona, which are less detailed but claim there was also a trace amount of beryllium:

By mass, 76% of the atoms in the Universe were Hydrogen, 24% were Helium, and only a trace was in the form of Lithium and Beryllium.

[Pleonast]

There was cosmological nucleosynthesis. Basically, the early universe was hot and dense enough for heavier elements to form, at least for a very short time.

Edit: simulpost!

This is a good place to mention the famous Alpher–Bethe–Gamow paper.

[Reply]

@Pleonast

This is a good place to mention the famous Alpher–Bethe–Gamow paper.

Hah! What an awesome, and terribly apropos, paper name. “In the beginning, there was Alpha.” And so on and so forth, I take it.

[Chronos]

For suitable values of “trace”, there were probably traces of just about everything. I would not be at all surprised if what’s now the visible Universe contained an atom or two of iron right from the beginning, for instance.

But for practical purposes, it was all hydrogen and helium. I think that the primordial supply of helium is still actually greater than that produced in stars.

EDIT:

Hah! What an awesome, and terribly apropos, paper name. “In the beginning, there was Alpha.” And so on and so forth, I take it.

Actually, Alpher and Gamow did most of the actual work on the theory; they invited Bethe (a renowned particle physicist) onto the project near the end, mostly for the sake of the name.