Expert: Courtney Seligman - 12/20/2008

Question
Describe how a proton found in hydrogen gas cloud(nebula), subsequently found itself in an atom of lead on the primitive earth.

things to consider- how can a element liked lead contain a proton from hydrogen? H gas cloud>8x star>Supernova>lead ejected.

How did the lead atom wind up on a planet around a main sequence star? Gas cloud formed by or enriched by supernova ejecta>Nebular Hypothesis

Answer
(Sorry for the delay in answering; but I'm on vacation, and won't have regular access to the Internet, until I return home.)

I presume, from the structure of your question, that you've copied a homework question, so I haven't followed the structure of the suggestions, as that is probably something you are supposed to do. However, I think the discussion below should make it easy to put the answer into any format you require. (If this wasn't a homework assignment, and you would like a more detailed discussion, just let me know, and I'll be happy to oblige you.)

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When the Universe was very young, it consisted only of hydrogen atoms; but over time, hydrogen was turned into heavier atoms, deep in the core of massive stars.

In the Sun and smaller stars, this process only turns the hydrogen into helium, and perhaps carbon; but for very massive stars, the process of building up smaller nuclei into larger ones (thermonuclear fusion) can create almost all the heavier atoms, up to iron. And when those stars supernova, all the even heavier elements are created, in the instant of their destruction.

The material of the exploding star is blown outwards, at very high velocities, and eventually mixes with the existing interstellar material, out of which new stars will eventually form. In the case of many stars, such as the Sun, some of the material also ends up in planets, such as the Earth. That's how the protons in various hydrogen atoms eventually end up as a lead nucleus, or for that matter, a uranium, gold or silver nucleus, in the Earth.

Courtney Seligman
Professor of Astronomy
Long Beach City College