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Hi Don,

It is possible for many different elements to have the same number of nucleons. It all comes down to isotopes. For example, Nickel has many stable isotopes such as 59Ni, 60Ni etc... What this means is that in each case the number of protons is the same but the number of neutrons changes.

And here I notice a mistake, in that I used Nickel 59, which is an unstable isotope, and it should have been Nickel 58 which is the most abundant isotope. Still the conclusion is the same, as cobalt is lower in the table than Nickel though is more massive because of more neutrons. Remember though that what defines the position of an element on the periodic table is not its total mass number, but its atomic number (that is the number of protons and electrons in the atom). It is this number that defines the chemical properties of the element and hence its position. For nuclei, you have to consider the total number of nucleons, and so the nuclear properties (akin to chemical reactions, but are instead nuclear reactions) is defined by the nucleon (or mass) number.

The reason why Cobalt has more neutrons than Nickel comes down to quantum mechanics, in particular to do with pauli exclusion principle. its rather difficult to explain, but it comes down to the "shell model" of the nucleus, where the number of protons and neutrons required to form a stable nucleus depends upon how each fill the proton and neutron and coupled proton/neutron shells. This is similar to the shell model of electron orbitals, though a bit more complex since you are dealing with two types of indistinguishable fermi-dirac particles.

In a very broad sense, inside the nucleus there are two competing forces, namely the mutual repulsion from electrostatic charges of the protons, and the attractive strong force between those protons, and the neutral neutrons. If you were to make a recipe of making nuclei, too many protons will cause the mixture to be unstable (the electrostatic force over comes the strong force), and to stabilise the mixture, you add neutrons. Sometimes though too many neutrons will make the mixture too flat, and so less are required. What defines the number of protons and neutrons in the recipe is quantum mechanics, and it inst always intuitive (Nickel is a nice example, as the 58 and 60 weight isotopes are stable, but the 59 mass isotope is not).

So many other nuclei can have the same number of nucleons (but different combionations). They are called isobars. Whilst some isobars will be stable and some unstable, some will have long half lives. An example is above where I mistakenly took Nickel59 and not Nickel 58.

I do remember that, but I dont think I have that data handy anymore. If I did, it would be on my previous and now expired computer. if I remember correctly the speed of sound values came from a journal article i found for you. I know for a fact that i do not have a copy of that article. I will though have a route around and see if I can find the information again.

Jonny




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Subject Views Written By Posted
Totally confused on The Periodic Table 1151 Ahatmose 05-Feb-12 03:39
Re: Totally confused on The Periodic Table 383 JonnyMcA 05-Feb-12 09:55
Re: Totally confused on The Periodic Table 270 Ahatmose 05-Feb-12 14:57
Re: Totally confused on The Periodic Table 356 JonnyMcA 05-Feb-12 15:52
Re: Totally confused on The Periodic Table 346 JonnyMcA 05-Feb-12 16:01
Re: Totally confused on The Periodic Table 309 Ahatmose 06-Feb-12 03:10
Re: Totally confused on The Periodic Table 312 JonnyMcA 06-Feb-12 18:26
Re: Totally confused on The Periodic Table 329 Spiros 05-Feb-12 22:00
Re: Totally confused on The Periodic Table 334 JonnyMcA 05-Feb-12 22:47
Re: Totally confused on The Periodic Table 327 Spiros 07-Feb-12 22:40
Re: Totally confused on The Periodic Table 327 Susan Doris 06-Feb-12 08:43
Re: Jonny/Ahatmose 360 Thunderbird 08-Feb-12 03:02
Index of Refraction 385 Ahatmose 09-Feb-12 03:08
Re: Index of Refraction 352 Ahatmose 09-Feb-12 03:25
Re: Index of Refraction 1333 JonnyMcA 09-Feb-12 08:34
Re: Index of Refraction 358 Ahatmose 09-Feb-12 16:10
Index of Refraction: The solution ? 404 Ahatmose 09-Feb-12 17:41
Re: Index of Refraction: The solution ? 362 JonnyMcA 11-Feb-12 09:03
Re: Index of Refraction 354 JonnyMcA 11-Feb-12 08:59
Re: Index of Refraction 342 Ahatmose 11-Feb-12 12:29
Re: Index of Refraction 390 JonnyMcA 11-Feb-12 14:12
Re: Index of Refraction 349 Ahatmose 12-Feb-12 13:11
Addendum: Index of Refraction 334 Ahatmose 12-Feb-12 13:19
Second Addendum: Index of Refraction 286 Ahatmose 12-Feb-12 13:26
Third Addendum: Index of Refraction 314 Ahatmose 12-Feb-12 13:32
Re: Third Addendum: Index of Refraction 321 JonnyMcA 12-Feb-12 16:03
Re: Third Addendum: Index of Refraction 336 JonnyMcA 12-Feb-12 21:17
Re: Second Addendum: Index of Refraction 342 JonnyMcA 12-Feb-12 15:40
Re: Addendum: Index of Refraction 322 JonnyMcA 12-Feb-12 15:34
Re: Index of Refraction 386 JonnyMcA 12-Feb-12 13:30
Re: Index of Refraction 323 Ahatmose 12-Feb-12 13:48
Re: Index of Refraction 336 JonnyMcA 12-Feb-12 15:32
Re: Index of Refraction 339 Ahatmose 13-Feb-12 01:23
Re: Index of Refraction 383 JonnyMcA 13-Feb-12 08:23
Re: Index of Refraction 365 Ahatmose 13-Feb-12 16:01
Re: Index of Refraction 362 JonnyMcA 13-Feb-12 19:01
Re: Index of Refraction 336 Ahatmose 13-Feb-12 16:47
Re: Index of Refraction 322 JonnyMcA 13-Feb-12 19:07
Re: Index of Refraction 334 Ahatmose 13-Feb-12 17:37
Re: Index of Refraction 322 JonnyMcA 13-Feb-12 19:20
Re: Index of Refraction 457 Spiros 05-Apr-18 14:20
Talk about stretching credibility: Index of Refraction 350 Ahatmose 13-Feb-12 05:48


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