Any theory that connects QM with physical properties?

[sigh hens]

by adding or subtracting protons and neutrons you get different atoms with completely different physical properties. Is there any theory that explains this connection?

[Tormod]

I don't understand your question. How does it relate to quantum mechanics? Sounds like chemistry to me. Can you elaborate?

[Pyrotex]

I don't understand your question. How does it relate to quantum mechanics? Sounds like chemistry to me. Can you elaborate?

 

It sounds to me like he needs to hear about 'emergent phenomena'.

[sigh hens]

I don't understand your question. How does it relate to quantum mechanics? Sounds like chemistry to me. Can you elaborate?

 

 

for example, an atom with 6 protons and 6 neutrons will have a melting point of 3652 degrees celsius, add another proton and another neutron and it will have a melting point of -210 degrees celsius. What is the connection between adding subatomic particles and the physical properties of the atom?

[Pyrotex]

for example, an atom with 6 protons and 6 neutrons will have a melting point of 3652 degrees celsius, add another proton and another neutron and it will have a melting point of -210 degrees celsius. What is the connection between adding subatomic particles and the physical properties of the atom?

 

I am probably unqualified to answer this one, but what the heck. I never let that stop me before. :cup:

 

The answer is -- there is hardly any connection between adding subatomic particles to the nucleus, and the physical properties of the atom. Or the connection is extremely subtle and unobvious.

 

When quarks combine to form protons and neutrons, these higher level objects (or phenomena) take on their own properties and obey a whole new set of rules that has very little if anything to do with the behavior of quarks. A proton is a new thing, in a new class of things, with a new set of properties.

 

Likewise, combine protons, neutrons and electrons, and you have a new-new thing, in a new-new class of things, with a new-new set of properties. These are called "emergent phenomena" -- atoms and atomic properties EMERGE out of the background, having newly EMERGED properties.

 

Likewise, the rules of chemistry that we observe when atoms of different kinds combine is yet another layer of "emergent phenomena". There is nothing about Oxygen and Hydrogen that can be used to <predict> all the properties of water. The boiling point of dimethyl-petro-dairy-sulfate (coffee creamer) has little if anything to do with the number of carbon atoms in it.

 

Likewise and finally, the rules of biology are "emergent phenomena". The behavior of a paramecium floating within the pond scum is not predictable from its chemistry. The paramecium is playing by a whole nuther set of rules.

[Tormod]

for example, an atom with 6 protons and 6 neutrons will have a melting point of 3652 degrees celsius, add another proton and another neutron and it will have a melting point of -210 degrees celsius. What is the connection between adding subatomic particles and the physical properties of the atom?

 

Chemistry is the science of the elements and their properties. Theoretical chemistry looks beyond the atom and looks at subatomic particles and tries to bring QM into chemistry.

 

Just adding and subtracting protons simply makes new isotopes, for example three oxygen atoms become ozone (O3). When an atom changes plike that it is bound to change properties as well, something we observe in nature. For elements that we cannot observe in isotopes (for any reason) we have to theorize about.

 

I still don't understand your question, however. Are you asking what are the forces that cause the atoms to change (ie the nuclear and electromagnetic forces)? Or are you asking why they change properties when they change?

 

Maybe this would be of interest to you:

http://en.wikipedia.org/wiki/Theoretical_chemistry

[sigh hens]

my question was about the connection between the constituents of an atom and the seeminly arbitrary properties that they produce. I think pyrotex answered it, basically saying that it is arbitrary. There is no way to predict the properties of an atom based on its constituents.

 

seems like a big gap in science.

[Tormod]

You're talking in riddles. The title of this topic regards quantum mechanics, and now you're talking about prediction of emergent properties. If there is a big gap in science, exactly where is it?

 

What you're asking is not something mystical and magical, it is what theoretical physicists and chemists have been studying for over a century.

 

The inner workings of the atom is not fully known, but we know quite a bit about it. Exactly why the atoms have the properties they have is a difficult question. I am not sure it is something that can be answered with a single "this is how it works". It's like asking "what is the physical property that makes it rain in Spain while it is night in New York" - ie, the two are not apparently related even though we could probably find a statistical correlation.

 

What properties are you talking about? Weight? Condictivity? Bose-einstein condensates?

 

That's why I call this chemistry.

 

The melting point, for example, is a point where the element goes through a phase change from solid to liquid or liquid to gas. It would be very strange if the boiling point simply changed on an even scale as we progress across the periodic table of elements, because atoms are complex and melting point is but one of the many properties they have. Thus we can say that melting point is not related to the number of protons and neutrons but rather it is related to the sum of other properties.

 

Try these sites for more information:

 

http://particleadventure.org/particleadventure/

 

http://www.chemicalelements.com/sup/help.html

[kamil]

by adding or subtracting protons and neutrons you get different atoms with completely different physical properties. Is there any theory that explains this connection?

 

Are you asking why do the elements differ only due to the amount of protons and neutrons?. Like that the difference between uranium and helium is that helium has two protons and uranium has 92.

[cwes99_03]

Just adding and subtracting protons simply makes new isotopes, for example three oxygen atoms become ozone (O3). When an atom changes plike that it is bound to change properties as well, something we observe in nature. For elements that we cannot observe in isotopes (for any reason) we have to theorize about.

 

Actually isotopes are the same element with different numbers of neutrons, not protons. O2 and O3 are allotropes.

 

Not having studied QM, I cannot say that there is any knowledge on why two different isotopes, or even two different elements have such vastly different properties. What is interesting is that the occur in groups and families (such as the alkali, metals, noble gasses, etc.) Maybe you should start there.

[Erasmus00]

by adding or subtracting protons and neutrons you get different atoms with completely different physical properties. Is there any theory that explains this connection?

 

Yes, actually, there is. But it has to do with the electrons more so then subatomic particles. If you add a proton to an element, in order to be electrically neutral, you must also add an electron.

 

Now, because of a physical property of electrons known as the Pauli exclusion principle, only one electron can occupy each energy level, so the new electron goes into a new energy level in the atom. The various properties of atoms follows from the patterns in energy levels predicted by quantum mechanics. The cyclic nature of these patterns also underlies the periodic table of elements.

-Will

[cwes99_03]

The various properties of atoms follows from the patterns in energy levels predicted by quantum mechanics. The cyclic nature of these patterns also underlies the periodic table of elements.

-Will

Will you are overstepping a bit here. Just having an extra electron does not change the properties as were mentioned earlier, namely the melting point and other things. Otherwise having an extra electron would mean that some metals suddenly become a gas. No, it is the extra quarks in the nucleus that change the properties of the element. How or why certain properties change the way they do, I am unaware of any theories.

The electron shells do cause some properties, but these are largely minimal compared to the other major differences between two elements. Afterall, a copper atom short one electron, is in no way similar to a nickel atom.

[Erasmus00]

Will you are overstepping a bit here. Just having an extra electron does not change the properties as were mentioned earlier, namely the melting point and other things.

 

Absolutely it does. What defines when an object begins to melt? The temperature at which electrostatic bonds begin to break. What controls the strength of these bonds? Mostly the electron structure of the atoms forming the bonds.

 

Otherwise having an extra electron would mean that some metals suddenly become a gas. No, it is the extra quarks in the nucleus that change the properties of the element. How or why certain properties change the way they do, I am unaware of any theories.

 

It is the neutral atoms that determine how bonds form. Adding extra electrons to a metal just adds an extra carrier electron to the already metallically bonded lattice atoms.

 

The electron shells do cause some properties, but these are largely minimal compared to the other major differences between two elements. Afterall, a copper atom short one electron, is in no way similar to a nickel atom.

 

In the absence of free negative particles, a copper atom short one electron behaves very much like a nickle atom. However, the left over positive charge creates a marked difference. Consider that single ionized helium and doubly ionized lithium behave very much like hydrogen.

-Will