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Offline krish1951

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Basic doubt in Particle Physics / QP
« on: 11/10/2011 08:07:27 »
Hi,

I do not have a science background, but have been fascinated about the nature of sub-atomic particles and the duality; energy exchange.

I need some patient explanation from someone on some (illiterate) basic questions:

1. If it is all about spinning particles around a nucleus - how do shells of atoms and subsequently molecules form? What are the 'outer covers' (akin to a skin of our body creating a boundary) formed?

2. Similarly the molecules and then the manifestation of the matter itself.

3. If it is all unstable projections in a space-time continuum, how do our own bodies stay intact, instead of dispersing into energy?

 [:I] Sorry if I sound too naive for this forum; I have been searching for a forum for non-scientists to ask questions and stumbled upon this forum. I am very happy if you refer me to basic reading material explaining the above.

Regards,
Krishnan 


 

Offline Soul Surfer

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« Reply #1 on: 11/10/2011 20:16:56 »
You have asked a lot of very big questions in your introduction and to answer them completely in one go would result in too long a reply and probably confuse you even more.  Could you please rephrase your question to ask only one simple question at a time and I will try to help you.
 

Offline krish1951

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« Reply #2 on: 11/10/2011 20:59:07 »
Thank you very much for your kind mail. Let me ask you one question first.

Example of one matter - ie element hydrogen. It gets built from quarks to particles then to atom and further on. First question is what is the boundary wall (outer casing) of an atom made of? How will each atom in a molecule be separately packaged to give an identity?   

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Offline Soul Surfer

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« Reply #3 on: 12/10/2011 09:45:01 »
That is a much more explainable question.

Firstly a hydrogen atom is made of two stable particles a proton and electron that are held together by the electromagnetic force of their opposite electrical charges which gets less by the inverse square law as distance increases

The electron is as far as is known at the moment a simple particle with no other structure than its charge and its spin. it is very light and because of this the quantum noise of uncertainty means that it cannot settle down and "stick to" the proton (the nucleus) and so "orbits" the proton (nucleus) in a fuzzy ball defining the outer surface of the atom it is this electron which interacts with other electrons in the outer surfaces of other atoms that creates all of chemistry and life.  The nuclei of atoms play almost no part in everyday life.  This electron cloud is what you describe as the outer casing of all atoms. 

In more complex atoms than hydrogen with several electrons the electron cloud has a complex uneven shape with lumps and bumps on it because of the nature of the electrons themselves.  The electrons of course repel each other because of their similar charge but they also attract each other because of the magnetic fields caused by their spins.

The size of the electron cloud around atoms is around 10^-10 of a meter.

The proton in the nucleus is a composite structure of three quarks held together by the strong nuclear force. This force is very different from the long range force of electrical charge it is more like an elastic band which gets stronger as you try to separate the particles and goes floppy and weak when they are close together.  The quarks are simple particles like the electrons but they are never seen on their own they are always grouped in twos and threes to make other particles.

The scale on which these forces act is around  10^-15 of a meter  so nuclei are very much smaller than the electron cloud in atoms.

 

Offline krish1951

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« Reply #4 on: 12/10/2011 10:30:33 »
So grateful for your clear reply; electrifying.

Am quoting from your reply:

"it is this electron which interacts with other electrons in the outer surfaces of other atoms that creates all of chemistry and life".

Casing is nothing but the furious spin of the electrons - and there is no physical barrier like a skin.
So all atoms in the molecules do not have boundaries. Firstly what stops these atoms of same element from interacting with each other of the same 'family' and say collapsing or forming a different 'bigger'atom?

As a corollary - why should similar atoms alone come together to form a homogeneous element (say hydrogen)? If the particles are spinning around, how do millions of these similarly defines atoms come together in one place to for that particular matter?

Appreciate your patient explaining - if too elementary, you have the option to make be read some basic material on these issues.

Regards 
 

Offline Soul Surfer

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« Reply #5 on: 12/10/2011 14:04:00 »
As you try to crush atoms together, the repulsion of the negatively charged electron cloud provides a very strong resistance and this prevents the atoms collapsing at normal temperatures and pressures but the atoms can still stick together because of the weaker magnetic attractions at the surface.  This results in our familiar solids and crystals where the atoms line up in regular patterns. 
As you heat solids up the atoms may start to slide over each other but still hold together and this is a liquid.  eventually when temperature is high enough the atoms fly around independently (or in fixed groups) in the case of molecular elements and compounds. n This is a gas if you get even hotter some or eventually all of the electrons can be shaken of the atoms  this is called a plasma  and is the state of the atoms in very hot places like stars.  this is compressible but the repulsion of the electrons makes it quite resilient  most stares are around the density of water  or less.  as the pressure increases up to a point when this gives way and the gas becomes what is known a degenerate where the atoms really are crushed.  This state exists in a white dwarf star  where densities can be many thousands of times greater than water.
 

Offline krish1951

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« Reply #6 on: 12/10/2011 14:15:41 »
Thank you. Sort of understand. However, a single atom of a matter x (say hydrogen) is an independent structure. Unless zillions of similar structured atoms come together to enable molecules of the similar matter x, that particular matter will not be formed in quantities for any practical use. How is it that zillions of similar structured atoms come together in a single place to cause formation of a matter which we use in our daily lives? Instead of randomly mixing with various types and structures of other atoms and floating around randomly? What is the reason for this 'family unity' to deliver various types of materials to us? Similarly, why would exact number of similar atoms join together to deliver a molecule?
 

Offline Soul Surfer

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« Reply #7 on: 12/10/2011 19:31:53 »
Let us take your example of hydrogen.  This is the most common atom in the universe two atoms of hydrogen attract each other strongly to form a diatomic molecule with a considerable release of energy.  once this has happened the molecules only attract each other quite weakly and so hydrogen gas does not liquefy until the temperature is only 20 degrees above absolute zero and hydrogen will solidify about six degrees cooler.

The next simplest nucleus is deuterium with one proton and one neutron.  This has very similar properties to hydrogen.  The properties of an atom are defined by the number of protons in the nucleus this determines the number of electrons required to neutralise the charge.  The second chemically different atom is helium with two protons and one or two neutrons.  Most stable nuclei have slightly more neutrons than protons because extra neutrons are needed to  help stick the neutrons together by the strong force.  The detailed structure and organisation of complex nuclei is currently only partly understood but is growing rapidly  Helium with two protons and two neutrons and two electrons is extremely stable and inert because all the charges and all the spins are balanced out.

Almost all nuclei larger than helium have been made inside stars by fusing simpler nuclei together to release energy to keep them shining.  They are released into space as the stars either evaporate or explode.  now as they are flying around in space atoms of certain types tend to stick together when they bump into each other depending on the temperature (speed of the atoms) and pressure  this creates the first differentiation and collection of similar atoms together.   Then when planets form these are further refined by periods of heating melting and cooling and reacting with other molecules like water hydrogen or oxygen to result in the sort of materials we find on the earth.

 

Offline krish1951

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« Reply #8 on: 12/10/2011 20:35:15 »
Thank you so much for your patience in explaining rudimentary science concepts for me to grasp; kindly let me know the line when I have extended my welcome. Some questions on your reply:

Two atoms of hydrogen attract each other strongly - Why should they stop with two? Why not 3 or 10 or whatever number? Why should attraction stop when exact number of 2 is achieved and in cases of other elements may  be 3 or 4?  How is this decided or determined?

Form a diatomic molecule with a considerable release of energy - each atom is a separate structure and similar atoms are attracted to each other for whatever reason - but why release of energy? there is no change in the structure or fusion or exchange of charge or any activity, except attraction?

Is there a scientific reason for similar atoms to be attracted to each other?

Is there any scientific basis or theory for each 'family' of atoms sticking together - like all Hydrogen or helium or even water coming together in a stream and not 'spilled' out in smaller lots all over the place?

Is there a compelling reason for the stars to continue the process of fission to shine? is it because once started the process is not stoppable?
 

Offline Soul Surfer

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« Reply #9 on: 12/10/2011 23:16:06 »
As I mentioned earlier because of their spins electrons generate a magnetic field like a little bar magnet.  the proton and electron cancel out the electrostatic field unless you are close to the electron orbital but the magnetic field extends further this means that two hydrogen atoms attract each other and stick together like a pair of bar magnets in a north south pole configuration.  Once this has happened the magnetic field is mostly cancelled out as well so a third hydrogen atom is not attracted very strongly.

If you hold a brick  and let it drop to the ground under gravity this releases energy.  You soon realise this if you drop it on your toe!  in fact both the brick and the ground get hotter at the impact point  the same is true for any two objects that are attracted to each other and hold themselves together by an attractive force.

Stars are formed when cold interstellar gas and dust (mostly hydrogen with a bit of helium and a tiny bit of other elements from previous dead stars) collapse under their own gravity.  As they do this the atoms collide with each other and release the energy as heat and the gas gets hotter and hotter until the outer layers start to glow and emit light just like white hot iron or a tungsten filament light bulb.  the compression continues until the internal pressure balances the weight of the gas above any point in the star.  this means that the gas in the middle is very compressed and very hot indeed,  millions of degrees C  at this temperature all the electrons are stripped from the atoms and the bare nuclei can collide with each other.  when hydrogen nuclei collide with some of the atoms of the dust they can sometimes fuse to make a larger nucleus and there is one preferred process that eventually turns four hydrogen nuclei into one helium nucleus with the release of a great deal of energy.  This happens just because the insides of stars get hot enough to do this and it is what happens when that material is at that temperature and pressure for long enough time.  A hydrogen bomb does it using a powerful explosion to compress material briefly to release this energy.

Most things in the universe happen because under whatever conditions exist at the time this is thew most probable thing that will happen because of the physical laws not because any one or any thing actually wants it to happen.
 

Offline krish1951

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« Reply #10 on: 13/10/2011 07:00:03 »
Thank you. Makes things clearer when I read your notes again and again.

One Q out of the above set - when 2 hydrogen atoms come together, they stick together due to magnetic force and the limit to the strength of the force determines the number of atoms and hence the particular molecule of the particular matter. However, why release of energy at this stage, as atoms are not compressed here?
 

Offline Soul Surfer

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« Reply #11 on: 13/10/2011 09:29:27 »
The release of energy is nothing to do with the "compression" or change of shape of the atoms.  It is due to the motion of the atoms in the attractive force field and creates kinetic energy that is released when the atoms come together.

The total energy of any closed system (for example the whole universe) is always constant it can only be changed from one form to another by the natural action of forces and motions within the closed system.

To go back to the dropped brick I mentioned earlier.  While I am holding the brick it has potential energy (it could drop) because I am preventing it falling in the earth's gravitational field.  When I let it go it starts to accelerate downward an this potential energy is converted into kinetic energy (energy due to motion)  when it hits the ground and stops it releases this kinetic energy mostly as heat and some of it as the sound of the brick hitting the ground.

When two hydrogen atoms stick together to form a molecule they do change shape because they form what is called a covalent bond.  The two electrons in effect orbit both hydrogen nuclei.  The release of energy from the molecule is in the form of one or more photons of electromagnetic radiation (light, heat etc)  If this energy was not released the molecule would be unstable and liable to fly apart because the hydrogen atoms would be moving around each other too quickly.  Fortunately it is quite easy for molecules forming to release energy as radiation.

It is interesting to note that this release of energy is not at all easy in the case of motion under gravity, as long as it does not involve collisions or gravitational interactions with other objects.   The orbits of planets and satellites.   So if a body from way out in the galaxy approaches the Sun it is most likely to swing around it in an open hyperbolic orbit and go away because it cannot lose the energy it gained as it approached.  This is also true for black holes.  It is very difficult to fall into a black hole unless you hit something else on the way there!
 

Offline krish1951

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« Reply #12 on: 14/10/2011 05:57:40 »
The two electrons in effect orbit both hydrogen nuclei - you mean both nuclei sort of stick together and now the orbit of the two electrons is around both as a single core? Which means in complex molecules of say 3 or 5 atoms, there will be only one core with 3 or 5 nuclei sitting adjacent to each other and the electrons spinning around all of these?
 

Offline Soul Surfer

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« Reply #13 on: 14/10/2011 08:41:15 »
It depends on the nature of the bonding involved.  I have greatly simplified what is a very complex and well researched process. 

The nuclei do not stick together because they repel each other very strongly electrostatically.  The electron cloud holds them together.  you cannot tell which electron is which or where they are but in this case the electron cloud becomes unified. This is called covalent bonding where the electrons are in effect shared.   In some molecules (or parts of molecules) electrons are transferred from one atom to the other  this is called electrovalent bonding.  There are other weaker bonds where because of their shape molecules key together.  This is often called hydrogen bonding because hydrogen atoms sticking off the edge of molecules link weakly.  This is why water is a liquid and determines how protein molecules with millions of atoms in them fold up into their specific and critical shapes.  Bonds can also oscillate between several options.
 

Offline krish1951

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« Reply #14 on: 14/10/2011 09:49:31 »
Is there enough advancement in Science now to un-bond atoms in a molecule? Will it become a reality - scientist making matter from particles by rearranging? How far are you from this and what are the hurdles for the same?
 

Offline syhprum

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« Reply #15 on: 14/10/2011 11:06:05 »
How much energy does the bonding of Hydrogen atoms into molecule's release ?, how does this compare with the formation of H2O molecule's from atomic Oxygen and Hydrogen molecule's?
 

Offline Soul Surfer

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« Reply #16 on: 14/10/2011 18:23:00 »
The restructuring of nuclei is done regularly using nuclear physics and several artificially created elements for example americium have commercial applications.  As for the un-bonding and re-bonding conventional molecules this is commonplace in chemistry and a basic function of life. The techniques used are called chemistry.  I am not quite sure what you are thinking about when you ask this question.
 
Nuclei and atoms cannot be connected together arbitrarily, they have to form a reasonably stable or metastable structure and this depends on how the bonding processes work. 

As I said above the chemical properties of elements are entirely determined by the number of electrons they have and this is always exactly equal to the number of protons that there are in the nucleus this is called the atomic number.

The total number of stable elements is strictly limited and almost certainly complete at 81 there are a few more that occur naturally even though they are slightly radioactive.  There are a greater number of unstable (radioactive) and they are all chemically similar to their non radioactive isotope counterparts.  The full number of chemically distinct elements stable or unstable is about 115 and increasing slowly as attempts are made to extend the list.

This page shows a graph showing all the stable and unstable elements  http://en.wikipedia.org/wiki/File:Isotopes_and_half-life.svg
« Last Edit: 14/10/2011 18:46:09 by Soul Surfer »
 

Offline krish1951

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« Reply #17 on: 15/10/2011 15:49:30 »
Thanks. When you talk of chemistry, I suppose you are talking about compounds being formed from molecules of elements. Was more asking about advancements in converting one base element into another by restructuring particles (alchemy sort of, or DNA altering equivalent)- is this still fantasy or is science moving towards the same?
 

Offline krish1951

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« Reply #18 on: 15/10/2011 15:50:06 »
I have a basic question again on  a related topic, which I will ask you in a new thread.
 

Offline Soul Surfer

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« Reply #19 on: 15/10/2011 19:03:09 »
Yes the transmutation of elements by nuclear physics has been commonplace and used on an industrial scale for more than sixty years it is just that the energy and effort involved in doing this is far too great for it to be used to generate rare elements unless the elements have extremely special properties. By far the greatest use of these processes is the transmutation of Uranium 238 into plutonium 239 using the radiation from a nuclear fission reactor for nuclear weapons manufacture.  It is definitely not worth turning other elements into gold for example.

All elements that are possible are known although the detailed chemical properties of the most unstable ones may not be fully investigated or fully investigable.
 

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« Reply #19 on: 15/10/2011 19:03:09 »

 

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