1. Established Member
Join Date
May 2004
Posts
671
I know how hydrogen fuses into helium than to carbon and so on and so forth until it ends up as iron. My question is how much hydrogen would it take to make iron? Im looking for a scale if you know what I mean.

2. Established Member
Join Date
Nov 2003
Posts
508
A typical Iron (Fe) atom has 56 - 57 times the mass of typical Hydrogen (H) atom... hmm never mind h34r:

3. Banned
Join Date
Nov 2003
Posts
1,233
It takes 56 atoms of Hydrogen to make one atom of Iron (Fe-56, the most abundant type of iron atom).

56 H -> 1 Fe-56 + Energy

This does not show the path, but it is a correct summary of the overall process.

The released Energy = 476 MeV for this process.

That is about 17 times the amount of Energy released in fusion of Hydrogen into Helium.

4 H -> 1 He-4 + 27.3 MeV

With kind regards,

Oliver
http://www.umr.edu/~om

4. Established Member
Join Date
May 2004
Posts
671
Wow Oliver, how long did it take to learn all that?

5. Not very. Just take the mass difference, multiply by c^2, and convert to MeV.
I&#39;m sure that in the middle of stars, all sorts of nuclear processes go on. The hydrogen to helium one is just much more prevalent.

6. Banned
Join Date
Nov 2003
Posts
1,233
ASEI is right, Bossman20081.

Basic nuclear science is simple.

Most energy comes from this very tiny region of space (about one millionth of one billionth of the size of an atom).

That is why I studied nuclear science.

With kind regards,

Oliver
http://www.umr.edu/~om

7. Established Member
Join Date
Feb 2004
Posts
2,746
but fascinating nonetheless

8. Established Member
Join Date
May 2004
Posts
671
I meant that if you know something like that you must have gone to school specifically for it. I wanted to know how long you went to school for it.

9. Banned
Join Date
Nov 2003
Posts
1,233
Thanks, Bossman20081.

I did not complete high school, but I managed to get into college in 1956.

Eight years later I started teaching here at the University of Missouri, after receiving a ** degree, a PhD degree, and some Postdoctoral Training.

During that period, I probably spent no more than 1.5 years actually studying nuclear science.

If you want to learn about nuclear science, I would be happy to help guide your efforts by e-mail.

Best wishes,

Oliver
http://www.umr.edu/~om

PS - Like water running downhill, nuclear reactions proceed spontaneously to the lowest potential energy per nucleon. This pdf file shows this most basic properties of the 2,850 different types of nuclei that are known.

10. Established Member
Join Date
May 2004
Posts
671
Well do you know the whole sequence of elements before hydrogen?

PS Wouldnt that make you a doctor?

11. Banned
Join Date
Nov 2003
Posts
1,233
There are about 110 elements known, Bossman20081, one more if you count the neutron as element #0. (I do. It also fits appropriately in the Periodic Table, above He, as the lightest noble gas.)

About 80 elements have at least one stable isotope - a particular mix of neutrons and protons. The remaining elements have only radioactive isotopes.

Element #1, Hydrogen, is the lightest of all. It has only 1 proton in its nucleus.

Element #2, Helium, is the next lightest element. It has 2 protons in its nucleus.

Element #26, Iron, is the most stable element. It has 26 protons in the nucleus.

Element #83, Bismuth, is the heaviest stable element. It has 83 protons in the nucleus.

Heavier elements are all radioactive, but some like Th and U decayed slowly and are still around.

Element #92, Uranium, is the heaviest element remaining today from the stellar nuclear reactions that made our elements about 5 billion years ago. It has 92 protons.

Element #90, Thorium, is still around, and decaying even slower than Uranium.

Element #94, Plutonium, was here at the birth of the solar system. We find its decay products in meteorites and trapped inside Earth.

For each element, we typically know of about 20 different isotopes (atoms with the same number of protons but different numbers of neutrons). Most of these have too many or too few neutrons and decay by emitting electrons or positrons.

Tin (Sn, element #50) has the most stable isotopes, ten.

All together, about 2,850 different types of nuclei are known today. Those are all shown in the "Cradle of the Nuclides".

With kind regards,

Oliver
http://www.umr.edu/~om

PS - Yes, I am sometimes called Doctor or Professor. But I am not personally fond of titles; sometimes rightfully called "sheepskins".

12. Established Member
Join Date
May 2004
Posts
671
Sorry, I messed up on my last post. I meant to say do you know the sequence of elements before iron in nuclear reactions. I would also like to know why some elements like uranium decay if you can.

Thanks.

13. Banned
Join Date
Nov 2003
Posts
1,233
If you can open and print pdf files, Bossman20081, please study the "Cradle of the Nuclides":

The low point in the valley is Iron-56 (Fe-56). That is the most stable nuclear configuration known.

Nuclear stability (low nuclear potential energy) depends mostly on interactions between neutrons (n) and protons (p) so there are:

- 1. Maximum n-p attractive interactions
- 2. Minimum n-n repulsive interactions
- 3. Minimum p-p repulsive interactions
- 4. Minimum repulsive interactions between + charges (Coulomb energy)

Item #4, Coulomb energy, becomes successively more important for heavy elements. To minimize Coulomb energy, heavy nuclei have higher n/p ratios. But that increases the number of n-n repulsive interactions. That is basically why Th, U, Pu and all other elements heavier than Bismuth decay.

We discuss this in "Attraction and repulsion of nucleons: Sources of Stellar Energy", J. Fusion Energy 19 (2002) 93-98

http://www.umr.edu/~om/abstracts/jfeinterbetnuc.pdf
http://www.umr.edu/~om/abstracts/jfeinterbetnuc.ps

With kind regards,

Oliver
http://www.umr.edu/~om

14. Established Member
Join Date
May 2004
Posts
671
Thanks Oliver for all the help. I appreciate it

15. Planetwatcher Guest
Okay, I can join this now that I found my source.
UNIVERSE second edition by Kaufmann and Freeman copyright 1968
Chapter 22 The Death of Stars page 438 table 22-1

I know it is a rather old source. Actually it is an old college level astronomy textbook I once picked up at a garage sale.
On the said page is a graph describing points in the chapter, which give nine specific steps before a star goes nova. Seven of these are increasing levels of nuclear fussion starting with hydrogen. Next is Helium, then Carbon, and Neon.
Followed by the reaction fusing into Oxygen, and Silicon.
Finally when the reaction produces iron, it can proceed no further.

You then have a collapse of the steller core, followed by a core bounce, and finally the explosion.
Now this isn&#39;t saying that a star can&#39;t produce iron, because it produces minute amounts of it throughout it&#39;s life, however, it is impossible to sustain a nuclear fussion reaction into iron, and it certainly won&#39;t burn it.

So if someone wants to use this to refute the iron sun argument as well, have at it, for the source is well documented.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•