Expert: Carlo Segre - 8/22/2011

Question
QUESTION: Dear Sir
Could you please tell me which was created first in the order of cosmological creation of elements and molecules: the element neon or the water molecule? If you could elaborate a little on this that would be excellent. This is not for homework, just amateur curiosity.
With thanks
Jeremy

ANSWER: Dear Jeremy:

You are actually asking about two completely different processes as water is a molecule and Neon is an atom.  A better question would be the sequence of creation of Hydrogen, Oxygen, and Neon.  Once you have Hydrogen and Oxygen, then formation of water is possible if the temperature is low enough.

In the Big Bang model of the universe, the first thing that is formed after the quark-gluon plasma is no longer stable (that is the universe has cooled down sufficiently) is the hydrogen nucleus (i.e. a proton).  When the temperature cools further, electrons bind to the protons to form Hydrogen atoms.  The atoms will then condense to form stars which sustain nuclear fusion, creating Helium nuclei and eventually heavier and heavier nuclei (not atoms) inside the stars.  When the stars explode in novae and supernovae, even heavier nuclei are formed and dispersed in such a way as is possible to form planets like the Earth.

Therefore, the answer to your question is that hydrogen is formed first and Oxygen nuclei can be formed inside a star but will not be atoms and will not generally form water until they are expelled from the star and are able to combine with hydrogen gas.  Neon is formed during the stellar explosions.

So, I suppose it is possible to find interstellar water before you might expect to have Neon.

Cheers,

Carlo


---------- FOLLOW-UP ----------

QUESTION: Dear Carlo
Thank you for your very helpful answer. However could you please explain if the Neon ATOM is formed DURING a stellar explosion, and the oxygen ATOM only after it cooled down why would not Neon come first?

Or  If only the Neon NUCLEI formed during the explosion, how long would it take to form a Neon ATOM. would that happen before or after Oxygen cooled down enough to form an atom and subsequently the water molecule?

Will  the oxygen nuclei form before the Neon nuclei because it is lighter?

I am interested partly because it seems Neon and Water have the same number of protons/electrons

Sorry to be persistent, I appreciate your time and knowledge

Jeremy

Answer
Hi Jeremy:

Your original question asked about the water MOLECULE, not the oxygen ATOM.  If you as me about oxygen and neon as atoms, then it is likely that oxygen is formed first, since it is possible in the last stages before going nova, a star is actually producing some heavier nuclei in the fusion process.  But these are only oxygen nuclei (not even atoms) because in the core of a star, the temperature is sufficiently high that all atoms are completely ionized and there is a plasma of electrons and nuclei.  You can see how water has no chance or forming in this environment as a molecule requires the presence of electrons to form bonds.  Neon atoms, or rather nuclei, can probably only form after a nova since the atomic number is sufficiently large.

So the answer is that the while the combined atomic number of H2O and Ne is the same, inside the core of a start a molecule cannot exist because of the temperature and since the ejection of nuclei from the core of a star requires a nova, then the neon nucleus, and then the atom upon cooling, will form before
the temperature is low enough to permit the formation of a molecule such as water.
Carlo